SCHEME OF WORK
WEEK TOPIC
1. Revision / Halogens
Electronic configuration
Position in the periodic table
2 & 3 Chlorine & laboratory preparation, properties, uses, test for chloride ion, compounds of halogens e.g. hydrogen chloride laboratory preparation, properties and uses. Comparison of solubility of HCl in water and in Toluene.
4. Nitrogen and its family - preparation, properties and uses
5 - 6 Compounds of Nitrogen i.e. Ammonia (NH3) - preparation, properties and uses
b. oxides of Nitrogen & NO, NO2, N2O their preparations, properties and uses
c. Trioxonitrate (V) acid (HNO3) & preparations, properties, uses
Test for nitrate (NO-)
7. Sulphur & extraction, allotropes and properties
8 & 9 Compound of sulphur: H2S, H2SO3, H2SO4 & preparations, properties and uses, test for S2-, SO32-, SO42-
10. Introduction to organic chemistry& classification of organic compounds
Homologous series
11 & 12 Revision
3RD TERM
WEEK 1
TOPIC: NON-METALS
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain how nitrogen occurs in nature
2. Explain the laboratory preparation of nitrogen
3. Explain the industrial preparation of nitrogen
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New edition)
CONTENT: NITROGEN
Nitrogen occurs chiefly in the free form of air, making up about 78% by volume of the atmosphere. Free nitrogen in air is important because it dilutes the oxygen to the point where combustion, respiration and oxidation of metals are reasonably slow. In the combined form, nitrogen occurs as trioxonitrates (v) of sodium and calcium, as well as ammonium salts (in the earth’s crust). Combined nitrogen is also found in organic matter such as proteins, urea and vitamin B compounds.
LABORATORY PREPARATION OF NITROGEN
(A) From air:
Nitrogen is obtained from air by removing other constituents. CO2 and O2 are removed by passing air through caustic soda and heated copper turnings respectively. But, the nitrogen obtained this way is denser than pure nitrogen because it contains about 1% by volume of noble gases as impurities.
Nitrogen can also be produced by the following chemical methods:
(B) From ammonium dioxonitrate(iii):
NaNO2(aq) + Nh4Cl(aq) NH4NO2(aq) + NaCl(aq)
NH4NO2(aq) N2(g) + 2H2O(l)
(C) From ammonium heptaoxodichromate (vi)
(NH4)2Cr2O7(s) Cr2O3(s) + 4H2O(l) + N2(g)
(D) From ammonia:
Nitrogen is liberated when ammonia is oxidized by hot copper (ii) oxide.
2NH3(g) + 3CuO(s) 3Cu(s) + 3H2O(g) +N2(g)
(E) From dinitrogen (i)oxide:
When dinitrogen (i) oxide is passed over red hot copper the gas is reduced to nitrogen.
N2O(g) +Cu(s) CuO(s) + N2(g)
INDUSTRIAL PREPARATION OF NITROGEN
Nitrogen is prepared industrially by the fractional distillation of liquid air.
Carbon (iv) oxide is removed from air and such air is liquefied by successive compression and cooling processes. Upon distillation, nitrogen gas is given off first at – 196oc (at s.p) and is separated from oxygen which boils at -183oc (at s.p). the nitrogen is stored in steel cylinders and sold as liquid nitrogen or as the compressed gas.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the occurrence of nitrogen in the free sate and in the combined form.
2. Explain the laboratory preparation of nitrogen from air.
3. Explain the industrial preparation of nitrogen.
ASSIGNMENT:
1. What is an aspirator bottle used for?
2. Balance the equation below:
NH3(g) + CuO(s) 3Cu(s) +H2O(g) + N2(g).
3. Explain how CO2 and O2 can be removed from air.
4. Why is the nitrogen produced from air in the laboratory denser than pure nitrogen?
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List the physical properties of nitrogen.
b. With the aid of balanced chemical equation, explain the chemical properties of nitrogen.
c. List and explain the uses of nitrogen.
CONTENT: PROPERTIES OF NITROGEN
PHYSICAL PROPERTIES:
1. Nitrogen is colourless, odourless and tasteless.
2. Pure nitrogen is slightly lighter than air.
3. It is only slightly soluble in water. Two volumes of the gas dissolve in 100 volumes of water at room temperature.
4. The melting point of nitrogen is -210oc and its boiling point is -196oc. these low temperatures are due to the weak Vander Waals forces which exist in the solid and liquid states.
CHEMICAL PROPERTIES:
Nitrogen occurs in Group V of the periodic table and it has five valence electrons. It can exist in oxidation states of -3 to +5 in its compounds. Nitrogen gas exists in air as a diatomic molecule with triple covalent bonds between its atoms (NEN).
OXIDATION STATES OF NITROGEN IN ITS COMPOUNDS
NAME OF COMPOUND
FORMULA
OXIDATION STATE
Ammonia
NH3
-3
Hydrazine
N2H4
-2
Hydroxylamine
NH2OH
-1
Nitrogen
N2
0
Dinitrogen (i) oxide
N2O
+1
Nitrogen (ii) oxide
NO
+2
Dinitrogen (iii) oxide
N2O3
+3
Dioxonitrate (iii)
NO2-
+3
Nitrogen (iv) oxide
NO2
+4
Dinitrogen (v) oxide
N2O5
+5
Trioxonitrate (v)
NO3-
+5
At very high temperatures and pressures, nitrogen combines directly with hydrogen, oxygen and certain metals.
(i) With metals:
Nitrogen combines directly with very electropositive metals, e.g. magnesium, calcium, aluminum and iron to form nitrides.
3Mg(s) + N2 (g) Mg3N2(s)
(Red hot)
The nitride is readily hydrolyzed when warm with water to give ammonia gas.
Mg3N2(s) + 6H2O(l) warm 3Mg(OH)2(s) + 2NH3(g)
(ii) With non-metals:
Nitrogen combines with hydrogen to form NH3.
Nitrogen also combines directly with oxygen at very high temperatures (about 20000c) or in the presence of a high voltage electric spark to form small amounts of NO. In nature, this reaction occurs in the atmosphere when lightning flashes.
N2(g) + O2(g) 2NO(g)
USES OF NITROGEN
1. Nitrogen is used in the industrial manufacture of ammonia, cyanide, Cyanamid and carbamide (an important fertilizer).
2. Liquid nitrogen is used as a cooling agent.
3. Nitrogen has an inert nature and is thus used
(a) As a carrier gas in gas chromatography;
(b) In providing an inert atmosphere for certain industrial processes involving easily oxidizable chemicals e.g. in making electronic components such as transistors, and in the annealing of metals
(c) As a preservative to prevent rancidity (due to the oxidation of fats) in packaged foods.
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List four physical properties of nitrogen
ii. Use chemical equation to explain the reaction of nitrogen with magnesium
iii. Write the equation for the reaction of nitrogen with oxygen.
ASSIGNMENT:
i. Determine the oxidation numbers of nitrogen in
a. N2O5
b. NH2OH
c. N2O
And hence give their IUPAC nomenclatures.
ii. Explain what is meant by the annealing of metals and the use of nitrogen gas in this process.
PERIOD: 3
SUB-TOPIC: AMMONIA (NH3)
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the nature of ammonia
2. Describe the laboratory preparation of ammonia with the aid of balanced chemical equations and diagram.
CONTENT:
Ammonia is a hydride of nitrogen. Natural ammonia is produced by the decomposition or decay of nitrogenous matter in the absence of air. The decomposition may be brought about by heat or putrefying bacteria. Thus, small traces of ammonia may be present in the air. But because of its great solubility in water, it rapidly dissolves in rain water and finds its way into the soil where it may be converted into other compounds.
LABORATORY PREPARATION OF AMMONIA
Ammonia is prepared in the laboratory by heating any ammonium salt with a non-volatile base (e.g. Ca(OH)2)
2NH4Cl(s) + Ca(OH)2(s) CaCl2(s) + 2H2O(l) + 2NH3(g)
Ca(OH)2 is preferred because it is cheap and not deliquescent like the caustic alkalis (KOH and NaOH), both reactants (NH4Cl and Ca(OH)2) are solids and should be thoroughly ground to provide the maximum surface area for reaction.
The common drying agents like conc. 2SO4 and fused CaCl2 are not suitable for drying ammonia because they react with the gas as shown below:
2NH3(g) + H2SO4(aq) (NH4)2SO4(s)
4NH3(g) + CaCl2 (s) CaCl2.4NH3(s)
The preferred drying agent for ammonia gas is calcium oxide, CaO, (quick lime) because it does not react with ammonia.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain how NH3 is produced naturally
2. Explain the laboratory preparation of NH3
3. Why can NH3 not be dried by conc. H2SO4 and fused Ca(OH)2.
ASSIGNMENT:
1. Write the balanced chemical equation for the reaction between NH4Cl and Ca(OH)2.
2. Why is it necessary to dry the ammonia gas produced in the laboratory?
PERIOD: 4
SUB-TOPIC: INDUSTRIAL PREPARATION OF AMMONIA
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the Haber process for the industrial manufacture of NH3 gas.
2. List the conditions necessary for maximum yield of NH3 gas.
3. Draw the Haber process diagram for the industrial preparation of ammonia.
CONTENT:
HABER PROCESS: is used to manufacture ammonia from nitrogen and hydrogen gases. Since the direct combination of nitrogen and hydrogen is a reversible reaction, special conditions of reaction are necessary for the optimum yield of ammonia
SPECIAL CONDITIONS OF REACTION FOR THE OPTIMUM YIELD OF AMMONIA (HABER PROCESS)
1. The Haber process involves mixing nitrogen and hydrogen in the volume ratio of 1:3 and passing the mixture
2. Over finely divided iron catalyst
3. At a temperature of about 450oc, and
4. A pressure of about 200 atmospheres.
The yield of ammonia is 15% under these conditions.
The ammonia is then liquefied by cooling and the unused gases are re-circulated over the catalyst for further production of ammonia.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the four conditions necessary for the optimum yield of ammonia using the Haber process.
2. Draw the Haber process chart for the industrial production of ammonia.
ASSIGNMENT:
1. State Le chatelier’s principle
2. Explain the effect of decrease in pressure on the equilibrium position in the Haber process for ammonia production.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain how nitrogen occurs in nature
2. Explain the laboratory preparation of nitrogen
3. Explain the industrial preparation of nitrogen
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New edition)
CONTENT: NITROGEN
Nitrogen occurs chiefly in the free form of air, making up about 78% by volume of the atmosphere. Free nitrogen in air is important because it dilutes the oxygen to the point where combustion, respiration and oxidation of metals are reasonably slow. In the combined form, nitrogen occurs as trioxonitrates (v) of sodium and calcium, as well as ammonium salts (in the earth’s crust). Combined nitrogen is also found in organic matter such as proteins, urea and vitamin B compounds.
LABORATORY PREPARATION OF NITROGEN
(A) From air:
Nitrogen is obtained from air by removing other constituents. CO2 and O2 are removed by passing air through caustic soda and heated copper turnings respectively. But, the nitrogen obtained this way is denser than pure nitrogen because it contains about 1% by volume of noble gases as impurities.
Nitrogen can also be produced by the following chemical methods:
(B) From ammonium dioxonitrate(iii):
NaNO2(aq) + Nh4Cl(aq) NH4NO2(aq) + NaCl(aq)
NH4NO2(aq) N2(g) + 2H2O(l)
(C) From ammonium heptaoxodichromate (vi)
(NH4)2Cr2O7(s) Cr2O3(s) + 4H2O(l) + N2(g)
(D) From ammonia:
Nitrogen is liberated when ammonia is oxidized by hot copper (ii) oxide.
2NH3(g) + 3CuO(s) 3Cu(s) + 3H2O(g) +N2(g)
(E) From dinitrogen (i)oxide:
When dinitrogen (i) oxide is passed over red hot copper the gas is reduced to nitrogen.
N2O(g) +Cu(s) CuO(s) + N2(g)
INDUSTRIAL PREPARATION OF NITROGEN
Nitrogen is prepared industrially by the fractional distillation of liquid air.
Carbon (iv) oxide is removed from air and such air is liquefied by successive compression and cooling processes. Upon distillation, nitrogen gas is given off first at – 196oc (at s.p) and is separated from oxygen which boils at -183oc (at s.p). the nitrogen is stored in steel cylinders and sold as liquid nitrogen or as the compressed gas.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the occurrence of nitrogen in the free sate and in the combined form.
2. Explain the laboratory preparation of nitrogen from air.
3. Explain the industrial preparation of nitrogen.
ASSIGNMENT:
1. What is an aspirator bottle used for?
2. Balance the equation below:
NH3(g) + CuO(s) 3Cu(s) +H2O(g) + N2(g).
3. Explain how CO2 and O2 can be removed from air.
4. Why is the nitrogen produced from air in the laboratory denser than pure nitrogen?
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List the physical properties of nitrogen.
b. With the aid of balanced chemical equation, explain the chemical properties of nitrogen.
c. List and explain the uses of nitrogen.
CONTENT: PROPERTIES OF NITROGEN
PHYSICAL PROPERTIES:
1. Nitrogen is colourless, odourless and tasteless.
2. Pure nitrogen is slightly lighter than air.
3. It is only slightly soluble in water. Two volumes of the gas dissolve in 100 volumes of water at room temperature.
4. The melting point of nitrogen is -210oc and its boiling point is -196oc. these low temperatures are due to the weak Vander Waals forces which exist in the solid and liquid states.
CHEMICAL PROPERTIES:
Nitrogen occurs in Group V of the periodic table and it has five valence electrons. It can exist in oxidation states of -3 to +5 in its compounds. Nitrogen gas exists in air as a diatomic molecule with triple covalent bonds between its atoms (NEN).
OXIDATION STATES OF NITROGEN IN ITS COMPOUNDS
NAME OF COMPOUND
FORMULA
OXIDATION STATE
Ammonia
NH3
-3
Hydrazine
N2H4
-2
Hydroxylamine
NH2OH
-1
Nitrogen
N2
0
Dinitrogen (i) oxide
N2O
+1
Nitrogen (ii) oxide
NO
+2
Dinitrogen (iii) oxide
N2O3
+3
Dioxonitrate (iii)
NO2-
+3
Nitrogen (iv) oxide
NO2
+4
Dinitrogen (v) oxide
N2O5
+5
Trioxonitrate (v)
NO3-
+5
At very high temperatures and pressures, nitrogen combines directly with hydrogen, oxygen and certain metals.
(i) With metals:
Nitrogen combines directly with very electropositive metals, e.g. magnesium, calcium, aluminum and iron to form nitrides.
3Mg(s) + N2 (g) Mg3N2(s)
(Red hot)
The nitride is readily hydrolyzed when warm with water to give ammonia gas.
Mg3N2(s) + 6H2O(l) warm 3Mg(OH)2(s) + 2NH3(g)
(ii) With non-metals:
Nitrogen combines with hydrogen to form NH3.
Nitrogen also combines directly with oxygen at very high temperatures (about 20000c) or in the presence of a high voltage electric spark to form small amounts of NO. In nature, this reaction occurs in the atmosphere when lightning flashes.
N2(g) + O2(g) 2NO(g)
USES OF NITROGEN
1. Nitrogen is used in the industrial manufacture of ammonia, cyanide, Cyanamid and carbamide (an important fertilizer).
2. Liquid nitrogen is used as a cooling agent.
3. Nitrogen has an inert nature and is thus used
(a) As a carrier gas in gas chromatography;
(b) In providing an inert atmosphere for certain industrial processes involving easily oxidizable chemicals e.g. in making electronic components such as transistors, and in the annealing of metals
(c) As a preservative to prevent rancidity (due to the oxidation of fats) in packaged foods.
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List four physical properties of nitrogen
ii. Use chemical equation to explain the reaction of nitrogen with magnesium
iii. Write the equation for the reaction of nitrogen with oxygen.
ASSIGNMENT:
i. Determine the oxidation numbers of nitrogen in
a. N2O5
b. NH2OH
c. N2O
And hence give their IUPAC nomenclatures.
ii. Explain what is meant by the annealing of metals and the use of nitrogen gas in this process.
PERIOD: 3
SUB-TOPIC: AMMONIA (NH3)
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the nature of ammonia
2. Describe the laboratory preparation of ammonia with the aid of balanced chemical equations and diagram.
CONTENT:
Ammonia is a hydride of nitrogen. Natural ammonia is produced by the decomposition or decay of nitrogenous matter in the absence of air. The decomposition may be brought about by heat or putrefying bacteria. Thus, small traces of ammonia may be present in the air. But because of its great solubility in water, it rapidly dissolves in rain water and finds its way into the soil where it may be converted into other compounds.
LABORATORY PREPARATION OF AMMONIA
Ammonia is prepared in the laboratory by heating any ammonium salt with a non-volatile base (e.g. Ca(OH)2)
2NH4Cl(s) + Ca(OH)2(s) CaCl2(s) + 2H2O(l) + 2NH3(g)
Ca(OH)2 is preferred because it is cheap and not deliquescent like the caustic alkalis (KOH and NaOH), both reactants (NH4Cl and Ca(OH)2) are solids and should be thoroughly ground to provide the maximum surface area for reaction.
The common drying agents like conc. 2SO4 and fused CaCl2 are not suitable for drying ammonia because they react with the gas as shown below:
2NH3(g) + H2SO4(aq) (NH4)2SO4(s)
4NH3(g) + CaCl2 (s) CaCl2.4NH3(s)
The preferred drying agent for ammonia gas is calcium oxide, CaO, (quick lime) because it does not react with ammonia.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain how NH3 is produced naturally
2. Explain the laboratory preparation of NH3
3. Why can NH3 not be dried by conc. H2SO4 and fused Ca(OH)2.
ASSIGNMENT:
1. Write the balanced chemical equation for the reaction between NH4Cl and Ca(OH)2.
2. Why is it necessary to dry the ammonia gas produced in the laboratory?
PERIOD: 4
SUB-TOPIC: INDUSTRIAL PREPARATION OF AMMONIA
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the Haber process for the industrial manufacture of NH3 gas.
2. List the conditions necessary for maximum yield of NH3 gas.
3. Draw the Haber process diagram for the industrial preparation of ammonia.
CONTENT:
HABER PROCESS: is used to manufacture ammonia from nitrogen and hydrogen gases. Since the direct combination of nitrogen and hydrogen is a reversible reaction, special conditions of reaction are necessary for the optimum yield of ammonia
SPECIAL CONDITIONS OF REACTION FOR THE OPTIMUM YIELD OF AMMONIA (HABER PROCESS)
1. The Haber process involves mixing nitrogen and hydrogen in the volume ratio of 1:3 and passing the mixture
2. Over finely divided iron catalyst
3. At a temperature of about 450oc, and
4. A pressure of about 200 atmospheres.
The yield of ammonia is 15% under these conditions.
The ammonia is then liquefied by cooling and the unused gases are re-circulated over the catalyst for further production of ammonia.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the four conditions necessary for the optimum yield of ammonia using the Haber process.
2. Draw the Haber process chart for the industrial production of ammonia.
ASSIGNMENT:
1. State Le chatelier’s principle
2. Explain the effect of decrease in pressure on the equilibrium position in the Haber process for ammonia production.
WEEK 2
TOPIC: HALOGENS (ELECTRONIC CONFIGURATION. POSTION IN THE PERIODIC TABLE)
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the meaning of halogens and show how they are the most reactive non-metals known
2. List the structural properties of the halogens and write their electronic configurations
3. Explain the great similarities in the properties of the halogens
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition);
CONTENT:
The halogens are elements in Group VII of the periodic table. HALOGENS mean SALT FORMER. Halogens are the most reactive non-metals known because they have seven valence electrons each, requiring one electron each to attain octet stability. The halogens are so reactive than the other non-metals in the environment that, in nature, they exist mainly as salts instead of as free elements.
The halogens have the same number of valence electrons of seven and this makes them to show great similarity in their properties.
STRUCTURAL PROPERTIES AND ELECTRONIC CONFIGURATION OF HALOGENS
HALOGEN
F2
Cl2
Br2
I2
ATOMIC NUMBER
9
17
35
53
ELECTRON SHELLS
K,L
K,L,M
K,L,M,N
K,L,M,N,O
ELECTRONIC CONFIGURATION
2,7
2,8,7
2,8,18,7
2,8,18,18,7
ELECTRONS IN OUTERMOST SHELL
7
7
7
7
Examples of halogens, in order of increasing atomic numbers are: Fluorine (9F), Chlorine (17Cl), Bromine (35Br), Iodine (53I) and Astatine (85At).
SIMILARITIES OF HALOGENS
1. They are all non-metals
2. They exist as diatomic molecules(Atomicity of two)
3. They are coloured
4. They ionize to form univalent negative ions (e.g. Cl + e- Cl-), which react with metallic ions to form electrovalent compounds (e.g. Na+Cl-)
5. Their hydrides are covalent gases at room temperature and dissolve readily in water to form acids.
EVALUATION:
1. Explain why the group VII elements are called halogens.
2. Give the reason why halogens have great similarity in their properties.
3. List and explain five similarities of the halogens.
4. List five members of the Group VII elements in order of their increasing atomic number.
ASSIGNMENT:
Write the electronic configurations of the following halogens:
1. 9F
2. 17Cl
3. 35Br
4. 53I
5. Use ionic equation to show how fluorine ionizes to become a negatively charged ion; indicate the electronic configurations of fluorine and its ion.
SUB-TOPIC: TRENDS EXHIBITED BY THE HALOGENS DOWN THE GROUP IN THE PERIODIC TABLE
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List and explain the trends exhibited by the halogens down the group in the periodic table.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition);
CONTENT:
The trends exhibited by the halogens down the group in the periodic table are as follows:
1. A change in state (at 25oc): fluorine and chlorine are gases; bromine is a liquid and Iodine is a solid.
2. Their colours become darker - fluorine is yellow, chlorine is greenish-yellow, bromine is reddish-black, and Iodine is black.
3. Their melting point and boiling point increase progressively.
4. The ease with which they ionize to form negative ions decreases; i.e. their electro negativity decreases. This is reflected by a decrease in their chemical reactivity.
For example
a. In their reactions with hydrogen to form hydrides - fluorine reacts explosively even in the dark, chlorine slowly, in diffuse light but explosively in bright light; bromine slowly in bright light; and Iodine slowly and in completely even in bright light.
b. In their displacement reactions, where each halogen displaces the one following it from a solution of the latter's salt as shown below:
F2(g) + 2NaCl(aq) 2NaF(aq) + Cl2(g)
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(g)
Br2(g) + 2NaI(aq) 2NaBr(aq) + I2(g)
EVALUATION:
1. Explain three physical trends shown by the halogens.
2. Explain the chemicals trend shown by the halogens down the group in the periodic table (i.e. electro negativity and group displacement reactions).
ASSIGNMENT:
1. Use chemical equations to show the chemical trend of group displacement.
2. Why is fluorine more reactive than chlorine?
SUB-TOPIC: PROPERTIES OF CHLORINE AS A TYPICAL HALOGEN
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the physical properties of chlorine as atypical halogen.
2. Explain the physical properties of chlorine as a typical halogen.
CONTENT:
PHYSICAL PROPERTIES OF CHLORINE
1. Chlorine is greenish-yellow gas with an unpleasant choking smell.
2. It is moderately soluble in water. About 2.3cm3 of it will dissolve in km3 of water at s.t.p.
3. It is about 2.5 times denser than air.
4. It can easily be liquefied under a pressure of about 6 atmospheres.
5. It is poisonous. As little as 20 parts per million of it in the air can damage the mucous lining of our lungs.
EVALUATION:
1. List the physical properties of chlorine
2. Explain the physical properties of chlorine
ASSIGNMENT:
1. Explain how chlorine is poisonous
2. How is chlorine liquefiable?
SUB-TOPIC: CHEMICAL PROPERTIES OF CHLORINE AS A TYPICAL HALOGEN
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the chemical properties of chlorine as a typical halogen.
2. Use chemical equations to support and explain the chemical properties of chlorine.
CONTENT:
1. Chlorine has seven valence electrons and is very reactive although not as reactive as fluorine. Chlorine forms negative ion, Cl-, by gaining electron in electrovalent compounds (e.g. NaCl, CaCl2) or by sharing a pair of electrons in a single covalent bond with another atom of fairly similar electonegativity (e.g. as in Cl-Cl and hydrogen chloride gas, H-Cl).
2. Displacement reactions down the group e.g
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(l)
Cl2(g) + 2HI(aq) 2HCl(aq) + I2(S)
Cl2(g) + 2NaI(aq) 2NaCl(aq) + I2(g)
3. (a) combination with non-metals:
H2(g) + Cl2(g) 2HCl(g)
(b) combination with metals (directly)
2Na(s) + Cl2(g) 2NaCl(s)
Zn(s) + Cl2(g) ZnCl2(s)
2Fe(s) + 3Cl2(g) 2FeCl3(s)
4. Reactions with hydrogen:
(a) With hydrocarbons
C10H18(l) + 9Cl2(g) 10C(s) + 18Hcl(g)
(b) CH4(g) + Cl2(g) CH3Cl(g) + HCl(g)
(c) With ammonia
2NH3(g) + 3Cl2(g) N2(g) + 6HCl(g)
6NH3(g) + 6HCl(g) 6NH4Cl(s)
(d) With H2S
H2S(g) + Cl2(g) 2HCl(g) + S(s)
(e) With water
Cl2(g) + H20(l) HCl(aq) + HOCl(aq)
2HOCl(aq) sunlight 2HCl(aq) + O2(g)
5. As oxidizing agent
2FeCl2(aq) + Cl2(g) 2FeCl3(aq)
Green yellow
6. As a bleaching agent:
HOCl(aq) HCl(aq) + [O]
Dye + [O] (dye + O)
Coloured colourless
EVALUATION:
1. List the chemical properties of chlorine as a typical halogen
2. Show with chemical equations, four of the chemical behaviour of chlorine as a typical halogen.
ASSIGNMENT:
1. Comment on the relative reactivities of fluoride, chlorine, bromine and iodine.
2. With the aid of a well balanced chemical equation, explain the oxidizing action of chlorine on iron (ii) chloride.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the meaning of halogens and show how they are the most reactive non-metals known
2. List the structural properties of the halogens and write their electronic configurations
3. Explain the great similarities in the properties of the halogens
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition);
CONTENT:
The halogens are elements in Group VII of the periodic table. HALOGENS mean SALT FORMER. Halogens are the most reactive non-metals known because they have seven valence electrons each, requiring one electron each to attain octet stability. The halogens are so reactive than the other non-metals in the environment that, in nature, they exist mainly as salts instead of as free elements.
The halogens have the same number of valence electrons of seven and this makes them to show great similarity in their properties.
STRUCTURAL PROPERTIES AND ELECTRONIC CONFIGURATION OF HALOGENS
HALOGEN
F2
Cl2
Br2
I2
ATOMIC NUMBER
9
17
35
53
ELECTRON SHELLS
K,L
K,L,M
K,L,M,N
K,L,M,N,O
ELECTRONIC CONFIGURATION
2,7
2,8,7
2,8,18,7
2,8,18,18,7
ELECTRONS IN OUTERMOST SHELL
7
7
7
7
Examples of halogens, in order of increasing atomic numbers are: Fluorine (9F), Chlorine (17Cl), Bromine (35Br), Iodine (53I) and Astatine (85At).
SIMILARITIES OF HALOGENS
1. They are all non-metals
2. They exist as diatomic molecules(Atomicity of two)
3. They are coloured
4. They ionize to form univalent negative ions (e.g. Cl + e- Cl-), which react with metallic ions to form electrovalent compounds (e.g. Na+Cl-)
5. Their hydrides are covalent gases at room temperature and dissolve readily in water to form acids.
EVALUATION:
1. Explain why the group VII elements are called halogens.
2. Give the reason why halogens have great similarity in their properties.
3. List and explain five similarities of the halogens.
4. List five members of the Group VII elements in order of their increasing atomic number.
ASSIGNMENT:
Write the electronic configurations of the following halogens:
1. 9F
2. 17Cl
3. 35Br
4. 53I
5. Use ionic equation to show how fluorine ionizes to become a negatively charged ion; indicate the electronic configurations of fluorine and its ion.
SUB-TOPIC: TRENDS EXHIBITED BY THE HALOGENS DOWN THE GROUP IN THE PERIODIC TABLE
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List and explain the trends exhibited by the halogens down the group in the periodic table.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition);
CONTENT:
The trends exhibited by the halogens down the group in the periodic table are as follows:
1. A change in state (at 25oc): fluorine and chlorine are gases; bromine is a liquid and Iodine is a solid.
2. Their colours become darker - fluorine is yellow, chlorine is greenish-yellow, bromine is reddish-black, and Iodine is black.
3. Their melting point and boiling point increase progressively.
4. The ease with which they ionize to form negative ions decreases; i.e. their electro negativity decreases. This is reflected by a decrease in their chemical reactivity.
For example
a. In their reactions with hydrogen to form hydrides - fluorine reacts explosively even in the dark, chlorine slowly, in diffuse light but explosively in bright light; bromine slowly in bright light; and Iodine slowly and in completely even in bright light.
b. In their displacement reactions, where each halogen displaces the one following it from a solution of the latter's salt as shown below:
F2(g) + 2NaCl(aq) 2NaF(aq) + Cl2(g)
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(g)
Br2(g) + 2NaI(aq) 2NaBr(aq) + I2(g)
EVALUATION:
1. Explain three physical trends shown by the halogens.
2. Explain the chemicals trend shown by the halogens down the group in the periodic table (i.e. electro negativity and group displacement reactions).
ASSIGNMENT:
1. Use chemical equations to show the chemical trend of group displacement.
2. Why is fluorine more reactive than chlorine?
SUB-TOPIC: PROPERTIES OF CHLORINE AS A TYPICAL HALOGEN
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the physical properties of chlorine as atypical halogen.
2. Explain the physical properties of chlorine as a typical halogen.
CONTENT:
PHYSICAL PROPERTIES OF CHLORINE
1. Chlorine is greenish-yellow gas with an unpleasant choking smell.
2. It is moderately soluble in water. About 2.3cm3 of it will dissolve in km3 of water at s.t.p.
3. It is about 2.5 times denser than air.
4. It can easily be liquefied under a pressure of about 6 atmospheres.
5. It is poisonous. As little as 20 parts per million of it in the air can damage the mucous lining of our lungs.
EVALUATION:
1. List the physical properties of chlorine
2. Explain the physical properties of chlorine
ASSIGNMENT:
1. Explain how chlorine is poisonous
2. How is chlorine liquefiable?
SUB-TOPIC: CHEMICAL PROPERTIES OF CHLORINE AS A TYPICAL HALOGEN
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the chemical properties of chlorine as a typical halogen.
2. Use chemical equations to support and explain the chemical properties of chlorine.
CONTENT:
1. Chlorine has seven valence electrons and is very reactive although not as reactive as fluorine. Chlorine forms negative ion, Cl-, by gaining electron in electrovalent compounds (e.g. NaCl, CaCl2) or by sharing a pair of electrons in a single covalent bond with another atom of fairly similar electonegativity (e.g. as in Cl-Cl and hydrogen chloride gas, H-Cl).
2. Displacement reactions down the group e.g
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(l)
Cl2(g) + 2HI(aq) 2HCl(aq) + I2(S)
Cl2(g) + 2NaI(aq) 2NaCl(aq) + I2(g)
3. (a) combination with non-metals:
H2(g) + Cl2(g) 2HCl(g)
(b) combination with metals (directly)
2Na(s) + Cl2(g) 2NaCl(s)
Zn(s) + Cl2(g) ZnCl2(s)
2Fe(s) + 3Cl2(g) 2FeCl3(s)
4. Reactions with hydrogen:
(a) With hydrocarbons
C10H18(l) + 9Cl2(g) 10C(s) + 18Hcl(g)
(b) CH4(g) + Cl2(g) CH3Cl(g) + HCl(g)
(c) With ammonia
2NH3(g) + 3Cl2(g) N2(g) + 6HCl(g)
6NH3(g) + 6HCl(g) 6NH4Cl(s)
(d) With H2S
H2S(g) + Cl2(g) 2HCl(g) + S(s)
(e) With water
Cl2(g) + H20(l) HCl(aq) + HOCl(aq)
2HOCl(aq) sunlight 2HCl(aq) + O2(g)
5. As oxidizing agent
2FeCl2(aq) + Cl2(g) 2FeCl3(aq)
Green yellow
6. As a bleaching agent:
HOCl(aq) HCl(aq) + [O]
Dye + [O] (dye + O)
Coloured colourless
EVALUATION:
1. List the chemical properties of chlorine as a typical halogen
2. Show with chemical equations, four of the chemical behaviour of chlorine as a typical halogen.
ASSIGNMENT:
1. Comment on the relative reactivities of fluoride, chlorine, bromine and iodine.
2. With the aid of a well balanced chemical equation, explain the oxidizing action of chlorine on iron (ii) chloride.
WEEK 3
TOPIC: CHLORINE
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Describe the occurrence of chlorine
2. Explain the laboratory and industrial preparation of chlorine
3. List the physical properties of chlorine
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition).
CONTENT:
Chlorine does not occur free in nature because it is too reactive. Instead it is found in the combined state as chlorides, and the most abundant of these is sodium chloride (NaCl) or common salt, which is found both in the sea and as salt deposits.
LABORATORY PREPARATION OF CHLORINE
It is by the oxidation of concentrated hydrochloric acid with an oxidizing agent such as MnO2 or KMnO4.
MnO2(s) + 4HCl(aq) heat MnCl2(aq) + 2H2O(l) + Cl2(g)
2KMnO4(aq) + 16HCl(aq) 2MnCl2(aq) + 2KCl(aq) + 8H2O(l) + 5Cl2(g)
INDUSTRIAL PREPARATION OF CHLORINE
Commercially, chlorine is manufactured by the electrolysis of :
1. Brine [NaCl(aq)] and
2. Chlorides of molten sodium, magnesium or calcium.
The chlorine is then liquefied and stored under pressure in a steel cylinder.
PHYSICAL PROPERTIES OF CHLORINE
1. It is a greenish-yellow gas with unpleasant choking smell.
2. It is about 2.5 times denser than air.
3. It is moderately soluble in water.
4. It can easily be liquefied under a pressure of about 6 atmospheres.
5. It is poisonous. As little as 20 parts per million of it in the air can damage the mucous lining of our lungs.
EVALUATION:
1. Describe the occurrence of chlorine
2. With the aid of chemical equations, explain the laboratory preparation of chlorine.
3. Briefly explain the industrial method of preparing chlorine.
4. List the physical properties of chlorine.
ASSIGNMENT:
1. How would you obtain a few jars of dry chlorine starting with common salt?
2. How is chlorine gas poisonous to human lungs?
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the chemical properties of chlorine with the aid of chemical equations.
2. Give the tests for chlorine.
3. List soluble and insoluble chlorides
4. Give the test for chloride ion
CONTENT:
CHEMICAL PROPERTIES OF CHLORINE
There are seven valence electrons in a chlorine atom. It is very reactive and attains octet stability either
a. By gaining an electron, usually from metals of Groups I and II, to form a negative ion, Cl- as in ionic compounds like NaCl2 and CaCl2 or
b. By sharing a pair of electrons in a single covalent bond with another atom, having a fairly similar electro negative value, as in gasoue chlorine, Cl - Cl, and hydrogen chloride gas, H - Cl.
(1) Chlorine can combine with metals and non-metals to form chlorides.
2Na(s) + Cl2(g) 2NaCl(s)
Zn(s) + Cl2(g) ZnCl2(s)
H2(g) + Cl2(g) 2HCl(g)
(2) It can displace bromine and iodine from solutions of their salts
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(l)
Cl2(g) + 2KI(aq) 2KCl(aq) + I2(s)
(3) Chlorine has a very strong affinity for water and hydrogen sulphide:
Cl2(g) + H2(l) HCl(aq) + HOCl(aq)
2HOCl(aq) sunlight 2HCl(aq) + O2(g)
H2S(g) + Cl2(g) 2HCl(g) + S(s)
(4) Chlorine is a powerful oxidizing agent in the presence of water, it is a strong bleaching agent, which bleaches by oxidation, and it reacts with alkalis to form trioxochlorates(v) or oxochlorates(I).
TEST FOR CHLORINE
Chlorine is a greenish-yellow gas, with an irritating smell. Its presence can be confirmed by:
1. Chlorine turns damp blue litmus paper pink and then bleaches it.
2. Chlorine turns starch-iodide paper dark blue because chlorine displaces iodine from iodide and the iodine liberated then turns the starch blue.
2KI(aq) + Cl2(g) 2HCl(aq) + I2(s)
SOLUBLE AND INSOLUBLE CHLORIDES
The soluble chlorides are: NaCl, MgCl2, CaCl2.
The insoluble chlorides are:
a. Copper (i) chloride CuCl
b. Mercury (i) chloride, Hg2Cl2 and
c. Silver chloride, AgCl
Lead (ii) chloride, PbCl2 is insoluble in cold water but dissolves gradually when warmed.
TEST FOR SOLUBLE CHLORIDES
SILVER TRIOXONITRATE (V) TEST [AgNO3 TEST]
Acidify the test solution with excess dil. HNO3 (to prevent the precipitation of other salts) and then add a few drops of AgNO3. A white precipitate of AgCl which readily dissolves in aqueous ammonia indicates the presence of a chloride.
Ag+NO3-(aq) + Cl-(aq) AgCl(s) + NO3-(aq)
This test can also be performed with lead (ii) trioxonitrate (v). a white precipitate of PbCl2 which dissolves when heated and reappears when cooled indicates the presence of a chloride.
Pb2+ (NO3-)2(aq) + 2Cl-(aq) PbCl2(s) + 2NO3-(aq)
EVALUATION:
1. Use chemical equations to show the combination reactions of chlorine with
a. Metals
b. Non-metals
2. Give two chemical tests for chlorine.
3. List soluble and insoluble chlorides
4. Give the chemical test for soluble chlorides.
ASSIGNMENT:
1. Use chemical equations to show how chlorine can displace iodine from a solution of its salt.
2. Explain how chlorine attains octet stability ionically and covalently using appropriate examples
3. Explain the chemical tests to identify chlorine ion, Cl-, in magnesium chloride MgCl2. Support tour explanation with an ionic equation.
SUB-TOPIC: CHLORINE GAS Cl2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the uses of chlorine
2. Explain the laboratory and industrial preparations of hydrogen chloride gas
CONTENT:
USES OF CHLORINE
1. Chlorine is used as a germicide in the sterilization of water because chlorine has an oxidizing nature.
2. As a bleaching agent for cotton, linen and wood pulp; although it is too strong for bleaching animal fibres like silk and wool.
3. Chlorine is used in the manufacture of important chemical compounds e.g. bleaching powder, HCl, KClO3 9used in making matches and fireworks), NaClO3(a weed killer), domestic antiseptics (acidified sodium oxochlorate (i) solution.
HYDROGEN CHLORIDE GAS
Hydrogen chloride exists as a gas at s.t.p when it is dissolved in water, it forms hydrochloric acid.
LABORATORY PREPARATION OF HYDROGEN CHLORIDE GAS
Hydrogen chloride gas is prepared in the laboratory by the action of conc. H2SO4 on sodium chloride.
NaCl(s) +H2SO4(aq) NaH2SO4(aq) + HCl(g)
NaCl(s) + NaHSO4(aq) Na2SO4(aq) + HCl(g)
The overall equation for the reaction can be represented as follows:
2aCl(s) + H2SO4(aq) Na2SO4(aq) + 2HCl(g)
INDUSTRIAL PREPARATION OF HYDROGEN CHLORIDE GAS
Hydrogen chloride is made in large amounts by the direct combination of hydrogen and chlorine gases gotten from the electrolysis of brine. This hydrogen chloride gas obtained by burning a jet of hydrogen in chlorine is very pure. It is dissolved in water to form hydrochloric acid.
H2(g) + Cl2 (g) 2Hcl(g)
EVALUATION:
1. List the uses of chlorine
2. Explain the laboratory preparation of hydrogen chloride gas with the aid of chemical equations.
3. Briefly explain the industrial preparation of hydrogen chloride gas
ASSIGNMENT:
1. Explain what happens when HCl(g) is dissolved in water.
2. What is the difference in the nature of combination of hydrogen chloride gas and its product of dissolution in water.
CONTENT: PHYSICAL PROPERTIES OF HYDROGEN CHLORIDE GAS.
1. Pure HCl is a colourless gas with a sharp irritating smell.
2. It turns damp blue litmus paper red, showing that it is acidic in aqueous solution.
3. It is about 1-25 times denser than air.
4. It is very soluble in water, forming an aqueous solution of hydrochloric acid.
5. Hydrogen chloride neither burns nor supports combustion. Hence, it extinguishes a burning splinter.
CHEMICAL PROPERTIES OF HYDROGEN CHLORIDE GAS
1. Direct combination with ammonia: When a gas jar of hydrogen chloride is inverted over a gas jar full of ammonia, dense white fumes are formed which are particles of solid ammonium chloride suspended in air.
HCl(g) + NH3(g) NH4Cl(g)
2. Reaction with metals: Hydrogen chloride reacts with many metals, especially when they are heated to form the respective chlorides and hydrogen.
Zn(s) + 2HCl(g) ZnCl2(s) + H2(g)
If the metal can form two chlorides; usually the lower chloride is formed
Fe(s) + 2HCl(g) FeCl2(s) + H2(g)
TEST FOR HYDROGEN CHLORIDE
If the unknown gas is colourless, has an irritating smell, fumes in moist air and turns blue litmus paper red, then it is probably hydrogen chloride. The following two tests confirm its presence.
(a) With ammonia: Place a glass rod dipped with ammonia solution at the mouth of a gas jar containing the unknown gas. If the gas is hydrogen chloride, dense white fumes composed of suspended particles of ammonium chloride are produced.
NH3(g) + HCl(g) NH4Cl(s)
(b) With silver trioxonitrate (v): Add a few drops of AgNO3 solution to a gas jar containing the unknown gas and shake. If the gas is Hydrogen chloride, a white precipitate of silver chloride will be formed. Instead of AgNO3, lead (II) trioxonitrate (v) can also be used.
EVALUATION:
1. List four physical properties of HCl gas.
2. Use chemical equations to explain the reactions of hydrogen chloride gas with metals and then with ammonia.
3. Briefly explain two chemical tests for hydrogen chloride gas.
ASSIGNMENT:
1. What is the effect of HCl gas on litmus paper?
2. Why is it necessary to moisten a litmus paper before using it to test for the acidity or alkalinity of a gas?
3. Describe the physical tests for hydrogen chloride gas.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Describe the occurrence of chlorine
2. Explain the laboratory and industrial preparation of chlorine
3. List the physical properties of chlorine
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO (New Edition).
CONTENT:
Chlorine does not occur free in nature because it is too reactive. Instead it is found in the combined state as chlorides, and the most abundant of these is sodium chloride (NaCl) or common salt, which is found both in the sea and as salt deposits.
LABORATORY PREPARATION OF CHLORINE
It is by the oxidation of concentrated hydrochloric acid with an oxidizing agent such as MnO2 or KMnO4.
MnO2(s) + 4HCl(aq) heat MnCl2(aq) + 2H2O(l) + Cl2(g)
2KMnO4(aq) + 16HCl(aq) 2MnCl2(aq) + 2KCl(aq) + 8H2O(l) + 5Cl2(g)
INDUSTRIAL PREPARATION OF CHLORINE
Commercially, chlorine is manufactured by the electrolysis of :
1. Brine [NaCl(aq)] and
2. Chlorides of molten sodium, magnesium or calcium.
The chlorine is then liquefied and stored under pressure in a steel cylinder.
PHYSICAL PROPERTIES OF CHLORINE
1. It is a greenish-yellow gas with unpleasant choking smell.
2. It is about 2.5 times denser than air.
3. It is moderately soluble in water.
4. It can easily be liquefied under a pressure of about 6 atmospheres.
5. It is poisonous. As little as 20 parts per million of it in the air can damage the mucous lining of our lungs.
EVALUATION:
1. Describe the occurrence of chlorine
2. With the aid of chemical equations, explain the laboratory preparation of chlorine.
3. Briefly explain the industrial method of preparing chlorine.
4. List the physical properties of chlorine.
ASSIGNMENT:
1. How would you obtain a few jars of dry chlorine starting with common salt?
2. How is chlorine gas poisonous to human lungs?
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Explain the chemical properties of chlorine with the aid of chemical equations.
2. Give the tests for chlorine.
3. List soluble and insoluble chlorides
4. Give the test for chloride ion
CONTENT:
CHEMICAL PROPERTIES OF CHLORINE
There are seven valence electrons in a chlorine atom. It is very reactive and attains octet stability either
a. By gaining an electron, usually from metals of Groups I and II, to form a negative ion, Cl- as in ionic compounds like NaCl2 and CaCl2 or
b. By sharing a pair of electrons in a single covalent bond with another atom, having a fairly similar electro negative value, as in gasoue chlorine, Cl - Cl, and hydrogen chloride gas, H - Cl.
(1) Chlorine can combine with metals and non-metals to form chlorides.
2Na(s) + Cl2(g) 2NaCl(s)
Zn(s) + Cl2(g) ZnCl2(s)
H2(g) + Cl2(g) 2HCl(g)
(2) It can displace bromine and iodine from solutions of their salts
Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(l)
Cl2(g) + 2KI(aq) 2KCl(aq) + I2(s)
(3) Chlorine has a very strong affinity for water and hydrogen sulphide:
Cl2(g) + H2(l) HCl(aq) + HOCl(aq)
2HOCl(aq) sunlight 2HCl(aq) + O2(g)
H2S(g) + Cl2(g) 2HCl(g) + S(s)
(4) Chlorine is a powerful oxidizing agent in the presence of water, it is a strong bleaching agent, which bleaches by oxidation, and it reacts with alkalis to form trioxochlorates(v) or oxochlorates(I).
TEST FOR CHLORINE
Chlorine is a greenish-yellow gas, with an irritating smell. Its presence can be confirmed by:
1. Chlorine turns damp blue litmus paper pink and then bleaches it.
2. Chlorine turns starch-iodide paper dark blue because chlorine displaces iodine from iodide and the iodine liberated then turns the starch blue.
2KI(aq) + Cl2(g) 2HCl(aq) + I2(s)
SOLUBLE AND INSOLUBLE CHLORIDES
The soluble chlorides are: NaCl, MgCl2, CaCl2.
The insoluble chlorides are:
a. Copper (i) chloride CuCl
b. Mercury (i) chloride, Hg2Cl2 and
c. Silver chloride, AgCl
Lead (ii) chloride, PbCl2 is insoluble in cold water but dissolves gradually when warmed.
TEST FOR SOLUBLE CHLORIDES
SILVER TRIOXONITRATE (V) TEST [AgNO3 TEST]
Acidify the test solution with excess dil. HNO3 (to prevent the precipitation of other salts) and then add a few drops of AgNO3. A white precipitate of AgCl which readily dissolves in aqueous ammonia indicates the presence of a chloride.
Ag+NO3-(aq) + Cl-(aq) AgCl(s) + NO3-(aq)
This test can also be performed with lead (ii) trioxonitrate (v). a white precipitate of PbCl2 which dissolves when heated and reappears when cooled indicates the presence of a chloride.
Pb2+ (NO3-)2(aq) + 2Cl-(aq) PbCl2(s) + 2NO3-(aq)
EVALUATION:
1. Use chemical equations to show the combination reactions of chlorine with
a. Metals
b. Non-metals
2. Give two chemical tests for chlorine.
3. List soluble and insoluble chlorides
4. Give the chemical test for soluble chlorides.
ASSIGNMENT:
1. Use chemical equations to show how chlorine can displace iodine from a solution of its salt.
2. Explain how chlorine attains octet stability ionically and covalently using appropriate examples
3. Explain the chemical tests to identify chlorine ion, Cl-, in magnesium chloride MgCl2. Support tour explanation with an ionic equation.
SUB-TOPIC: CHLORINE GAS Cl2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the uses of chlorine
2. Explain the laboratory and industrial preparations of hydrogen chloride gas
CONTENT:
USES OF CHLORINE
1. Chlorine is used as a germicide in the sterilization of water because chlorine has an oxidizing nature.
2. As a bleaching agent for cotton, linen and wood pulp; although it is too strong for bleaching animal fibres like silk and wool.
3. Chlorine is used in the manufacture of important chemical compounds e.g. bleaching powder, HCl, KClO3 9used in making matches and fireworks), NaClO3(a weed killer), domestic antiseptics (acidified sodium oxochlorate (i) solution.
HYDROGEN CHLORIDE GAS
Hydrogen chloride exists as a gas at s.t.p when it is dissolved in water, it forms hydrochloric acid.
LABORATORY PREPARATION OF HYDROGEN CHLORIDE GAS
Hydrogen chloride gas is prepared in the laboratory by the action of conc. H2SO4 on sodium chloride.
NaCl(s) +H2SO4(aq) NaH2SO4(aq) + HCl(g)
NaCl(s) + NaHSO4(aq) Na2SO4(aq) + HCl(g)
The overall equation for the reaction can be represented as follows:
2aCl(s) + H2SO4(aq) Na2SO4(aq) + 2HCl(g)
INDUSTRIAL PREPARATION OF HYDROGEN CHLORIDE GAS
Hydrogen chloride is made in large amounts by the direct combination of hydrogen and chlorine gases gotten from the electrolysis of brine. This hydrogen chloride gas obtained by burning a jet of hydrogen in chlorine is very pure. It is dissolved in water to form hydrochloric acid.
H2(g) + Cl2 (g) 2Hcl(g)
EVALUATION:
1. List the uses of chlorine
2. Explain the laboratory preparation of hydrogen chloride gas with the aid of chemical equations.
3. Briefly explain the industrial preparation of hydrogen chloride gas
ASSIGNMENT:
1. Explain what happens when HCl(g) is dissolved in water.
2. What is the difference in the nature of combination of hydrogen chloride gas and its product of dissolution in water.
CONTENT: PHYSICAL PROPERTIES OF HYDROGEN CHLORIDE GAS.
1. Pure HCl is a colourless gas with a sharp irritating smell.
2. It turns damp blue litmus paper red, showing that it is acidic in aqueous solution.
3. It is about 1-25 times denser than air.
4. It is very soluble in water, forming an aqueous solution of hydrochloric acid.
5. Hydrogen chloride neither burns nor supports combustion. Hence, it extinguishes a burning splinter.
CHEMICAL PROPERTIES OF HYDROGEN CHLORIDE GAS
1. Direct combination with ammonia: When a gas jar of hydrogen chloride is inverted over a gas jar full of ammonia, dense white fumes are formed which are particles of solid ammonium chloride suspended in air.
HCl(g) + NH3(g) NH4Cl(g)
2. Reaction with metals: Hydrogen chloride reacts with many metals, especially when they are heated to form the respective chlorides and hydrogen.
Zn(s) + 2HCl(g) ZnCl2(s) + H2(g)
If the metal can form two chlorides; usually the lower chloride is formed
Fe(s) + 2HCl(g) FeCl2(s) + H2(g)
TEST FOR HYDROGEN CHLORIDE
If the unknown gas is colourless, has an irritating smell, fumes in moist air and turns blue litmus paper red, then it is probably hydrogen chloride. The following two tests confirm its presence.
(a) With ammonia: Place a glass rod dipped with ammonia solution at the mouth of a gas jar containing the unknown gas. If the gas is hydrogen chloride, dense white fumes composed of suspended particles of ammonium chloride are produced.
NH3(g) + HCl(g) NH4Cl(s)
(b) With silver trioxonitrate (v): Add a few drops of AgNO3 solution to a gas jar containing the unknown gas and shake. If the gas is Hydrogen chloride, a white precipitate of silver chloride will be formed. Instead of AgNO3, lead (II) trioxonitrate (v) can also be used.
EVALUATION:
1. List four physical properties of HCl gas.
2. Use chemical equations to explain the reactions of hydrogen chloride gas with metals and then with ammonia.
3. Briefly explain two chemical tests for hydrogen chloride gas.
ASSIGNMENT:
1. What is the effect of HCl gas on litmus paper?
2. Why is it necessary to moisten a litmus paper before using it to test for the acidity or alkalinity of a gas?
3. Describe the physical tests for hydrogen chloride gas.
WEEK 4
TOPIC: NON-METALS
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Compare the solubility of dry hydrogen chloride in water and in toluene.
2. List and explain the uses of Hcl gas and Hcl acid.
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: COMPARISON OF SOLUBILITY OF HCL IN WATER AND IN TOLUENE (METHYL BENZENE)
Dry hydrogen chloride gas readily dissolves in non-polar solvents like chloroform and toluene but such a solution does not conduct electricity and has no acidic properties. This is due to the fact that hydrogen chloride, which is a covalent molecule, does not ionize when it dissolves in non-polar solvents.
In aqueous solution, it reacts with the polar water molecules and ionizes to form chloride and oxonium ions. The oxonium ions (H3O+) are responsible for the acidic properties of an aqueoue solution of the gas.
Hcl(g) + H2O(l) H3O+(aq) + Cl-(aq)
Hcl gas forms misty fumes in moist air because it dissolves in the moisture to form tiny droplets of hydrochloric acid.
USES OF HCL GAS AND HCL ACID
1. Hcl gas is used in the synthesis of chloroethene, an important component of some plastics.
2. Gelatin and glue from the tendons of animals are manufactured with the use of hydrochloric acid. Also, hydrochloric acid is used in the production of glucose from starch, as well as in the manufacture of textiles and dyes.
3. Hcl acid is used to remove oxides from metals prior to electroplating. This process is called PICKLING and is used in the steel making industry.
4. Hcl acid is used in the laboratory for the testing, analysis and preparation of other compounds.
EVALUATION:
1. Compare the properties of Hcl gas when dissolved in toluene and when dissolved in water.
2. List the uses of Hcl gas and Hcl acid.
ASSIGNMENT:
1. Briefly explain how Hcl acid is used to produce glucose from starch.
2. Use bonding to differentiate between Hcl gas and Hcl acid.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the properties of hydrochloric acid.
CONTENT: PROPERTIES OF HYDROCHLORIC ACID
1. ACTION OF HEAT: When conc. Hcl acid is heated, it boils, liberating hydrogen chloride fumes, making the solution to be more concentrated. In both cases, the solutions will boil until they contain about 20.24% hydrochloric acid. This solution is known as a CONSTANT BOILING MIXTURE or an AZEOTROPIC MIXTURE because any further heating will not affect its concentration.
2. AS AN ACID: Hcl gas dissolves in water to form hydrochloric acid which exhibits all the usual properties of acids.
(a) With metals: Metals which are more electro positive than hydrogen will liberate hydrogen gas from the acid, e.g.
Zn(s) + 2Hcl(aq) ZnCl2(aq) + H2(g)
(b) With bases:
ZnO(s) + 2Hcl(aq) ZnCl2(aq) + H2O(l)
NaOH(aq) + Hcl(aq) NaCl(aq) + H20(l)
(c) With trioxocarbonates (iv):
2HCl(aq) + >Na2CO3(s) 2NaCl(aq) + H2O(l) + CO2(g)
HCl(aq) + NaOHCO3(s) NaCl(aq) + H2O(l) + CO2(g)
EVALUATION:
i. Explain constant boiling mixture or azeotropic mixture as it relates to the action of heat on HCl acid.
ii. Use chemical equations to explain the property of HCl as an acid which can react with metals, bases ad trioxocarbonates (iv).
ASSIGNMENT:
Write the balanced chemical equations between:
i. Hydrochloric acid and Potassium trioxocarbonate (iv).
ii. Hydrochloric acid and Calcium hydroxide.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the properties of hydrochloric acid.
b. Briefly explain the methods of recovering chlorides from their solutions.
CONTENT: PROPERTIES OF HYDROCHLORIC ACID
3. As a precipitating agent:
AgNO3(aq) + HCl(aq) AgCl(s) + HNO3(aq)
Pb(NO3)2 (aq) + HCl(aq) PbCl2(s) + 2HNO3(aq)
4. Reactions with Oxidizing agents:
Conc. HCl is easily oxidized by strong oxidizing agents, such as KMnO4 to liberate chlorine. This is why HCl acid is never used to acidify solutions of oxidizing agents. Instead, tetraoxosulphate (vi) acid is used.
RECOVERY OF CHLORIDES FROM THEIR SOLUTIONS
Chlorides are not decomposed by heat. As a result, chlorides can be recovered by the evaporation of their solutions to dryness. Sometimes, they are also separated from their solutions by crystallization.
EVALUATION:
1. Explain the property of HCl as a precipitating agent, with the aid of chemical equations.
2. Explain how chlorides can be recovered from their solutions.
ASSIGNMENT:
i. Describe the process of evaporation to dryness.
ii. Briefly explain crystallization.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
Use chemical equations to explain the properties of chlorides.
CONTENT: PROPERTIES OF CHLORIDES
1. Action of Heat: Chlorides are not decomposed by heat. This makes them to be used in flame tests where the metals are identified by the colours of their flames.
2. With Tetraoxosulphate (vi) Acid: All chlorides react with hot conc. H2SO4 to produce HCl gas.
e.g. 2KCl(s) + H2SO4(aq) K2SO4(aq) + 2HCl(g)
2Cl-(s) + (H+)2SO42-(aq) SO42-(aq) + 2HCl(g)
When a metallic chloride is heated with conc. H2SO4 and a strong oxidizing agent, chlorine is produced.
2Cl-(S) + Mn4+ (O2-)2(s) + 4H+(aq) Mn2+(aq) + 2H2O(l) + Cl2(g)
EVALUATION:
1. List and explain the properties of chlorides.
2. Use chemical equations to show the reaction of chlorides with tetraoxosulphate (vi) acid ( hot conc.)
ASSIGNMENT:
i. Describe what happens when a glass rod is dipped into conc. HCl acid and then held at the mouth of a jar of ammonia. Give the equation of the reaction.
ii. Describe the effect of heat on dilute and concentrated hydrochloric acid respectively.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Compare the solubility of dry hydrogen chloride in water and in toluene.
2. List and explain the uses of Hcl gas and Hcl acid.
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: COMPARISON OF SOLUBILITY OF HCL IN WATER AND IN TOLUENE (METHYL BENZENE)
Dry hydrogen chloride gas readily dissolves in non-polar solvents like chloroform and toluene but such a solution does not conduct electricity and has no acidic properties. This is due to the fact that hydrogen chloride, which is a covalent molecule, does not ionize when it dissolves in non-polar solvents.
In aqueous solution, it reacts with the polar water molecules and ionizes to form chloride and oxonium ions. The oxonium ions (H3O+) are responsible for the acidic properties of an aqueoue solution of the gas.
Hcl(g) + H2O(l) H3O+(aq) + Cl-(aq)
Hcl gas forms misty fumes in moist air because it dissolves in the moisture to form tiny droplets of hydrochloric acid.
USES OF HCL GAS AND HCL ACID
1. Hcl gas is used in the synthesis of chloroethene, an important component of some plastics.
2. Gelatin and glue from the tendons of animals are manufactured with the use of hydrochloric acid. Also, hydrochloric acid is used in the production of glucose from starch, as well as in the manufacture of textiles and dyes.
3. Hcl acid is used to remove oxides from metals prior to electroplating. This process is called PICKLING and is used in the steel making industry.
4. Hcl acid is used in the laboratory for the testing, analysis and preparation of other compounds.
EVALUATION:
1. Compare the properties of Hcl gas when dissolved in toluene and when dissolved in water.
2. List the uses of Hcl gas and Hcl acid.
ASSIGNMENT:
1. Briefly explain how Hcl acid is used to produce glucose from starch.
2. Use bonding to differentiate between Hcl gas and Hcl acid.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the properties of hydrochloric acid.
CONTENT: PROPERTIES OF HYDROCHLORIC ACID
1. ACTION OF HEAT: When conc. Hcl acid is heated, it boils, liberating hydrogen chloride fumes, making the solution to be more concentrated. In both cases, the solutions will boil until they contain about 20.24% hydrochloric acid. This solution is known as a CONSTANT BOILING MIXTURE or an AZEOTROPIC MIXTURE because any further heating will not affect its concentration.
2. AS AN ACID: Hcl gas dissolves in water to form hydrochloric acid which exhibits all the usual properties of acids.
(a) With metals: Metals which are more electro positive than hydrogen will liberate hydrogen gas from the acid, e.g.
Zn(s) + 2Hcl(aq) ZnCl2(aq) + H2(g)
(b) With bases:
ZnO(s) + 2Hcl(aq) ZnCl2(aq) + H2O(l)
NaOH(aq) + Hcl(aq) NaCl(aq) + H20(l)
(c) With trioxocarbonates (iv):
2HCl(aq) + >Na2CO3(s) 2NaCl(aq) + H2O(l) + CO2(g)
HCl(aq) + NaOHCO3(s) NaCl(aq) + H2O(l) + CO2(g)
EVALUATION:
i. Explain constant boiling mixture or azeotropic mixture as it relates to the action of heat on HCl acid.
ii. Use chemical equations to explain the property of HCl as an acid which can react with metals, bases ad trioxocarbonates (iv).
ASSIGNMENT:
Write the balanced chemical equations between:
i. Hydrochloric acid and Potassium trioxocarbonate (iv).
ii. Hydrochloric acid and Calcium hydroxide.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the properties of hydrochloric acid.
b. Briefly explain the methods of recovering chlorides from their solutions.
CONTENT: PROPERTIES OF HYDROCHLORIC ACID
3. As a precipitating agent:
AgNO3(aq) + HCl(aq) AgCl(s) + HNO3(aq)
Pb(NO3)2 (aq) + HCl(aq) PbCl2(s) + 2HNO3(aq)
4. Reactions with Oxidizing agents:
Conc. HCl is easily oxidized by strong oxidizing agents, such as KMnO4 to liberate chlorine. This is why HCl acid is never used to acidify solutions of oxidizing agents. Instead, tetraoxosulphate (vi) acid is used.
RECOVERY OF CHLORIDES FROM THEIR SOLUTIONS
Chlorides are not decomposed by heat. As a result, chlorides can be recovered by the evaporation of their solutions to dryness. Sometimes, they are also separated from their solutions by crystallization.
EVALUATION:
1. Explain the property of HCl as a precipitating agent, with the aid of chemical equations.
2. Explain how chlorides can be recovered from their solutions.
ASSIGNMENT:
i. Describe the process of evaporation to dryness.
ii. Briefly explain crystallization.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
Use chemical equations to explain the properties of chlorides.
CONTENT: PROPERTIES OF CHLORIDES
1. Action of Heat: Chlorides are not decomposed by heat. This makes them to be used in flame tests where the metals are identified by the colours of their flames.
2. With Tetraoxosulphate (vi) Acid: All chlorides react with hot conc. H2SO4 to produce HCl gas.
e.g. 2KCl(s) + H2SO4(aq) K2SO4(aq) + 2HCl(g)
2Cl-(s) + (H+)2SO42-(aq) SO42-(aq) + 2HCl(g)
When a metallic chloride is heated with conc. H2SO4 and a strong oxidizing agent, chlorine is produced.
2Cl-(S) + Mn4+ (O2-)2(s) + 4H+(aq) Mn2+(aq) + 2H2O(l) + Cl2(g)
EVALUATION:
1. List and explain the properties of chlorides.
2. Use chemical equations to show the reaction of chlorides with tetraoxosulphate (vi) acid ( hot conc.)
ASSIGNMENT:
i. Describe what happens when a glass rod is dipped into conc. HCl acid and then held at the mouth of a jar of ammonia. Give the equation of the reaction.
ii. Describe the effect of heat on dilute and concentrated hydrochloric acid respectively.
WEEK 5
TOPIC: NITROGEN AND ITS COMPOUNDS
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the occurrence of nitrogen.
b. Describe the laboratory preparation of nitrogen with the aid of chemical equations and diagrams.
c. Explain the industrial preparation of nitrogen.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: OCCURRENCE OF NITROGEN
Nitrogen occurs chiefly in the free form in air, making up about 78% by volume of the atmosphere. Free nitrogen in air is important because it dilutes the oxygen to the point where combustion, respiration and oxidation of metals are reasonably slow. In the combined form, nitrogen occurs as trioxonitrates(v) of sodium and calcium, as well as ammonium salts (in the earth's crust) combined nitrogen is also found in organic matter such as proteins, urea and vitamin B compounds.
LABORATORY PREPARATION OF NITROGEN
A) From air:
Nitrogen is obtained from air by removing other constituents. CO2 and O2 are removed by passing air through caustic soda and heated copper turnings respectively. But, the nitrogen obtained this way is denser than pure nitrogen because it contains about 1% by volume of noble gases as impurities.
Nitrogen can also be prepared by the following chemical methods:
B) From ammonium dioxonitrate (iii)
NaNO2(aq) + NH4Cl(aq) NH4NO2(aq) + NaCl(aq)
NH4NO2(aq) 2H2O(l) + N2(g)
C) From ammonium heptaoxodichromate (vi)
(NH4)2Cr2O7(s) Cr2O3(s) + 4H2O (l) + N2 (g)
D) From ammonia: Nitrogen is liberated when ammonia is oxidized by hot copper (ii) oxide
2NH3 (g) + 3CUO(s) 3CU(s) + 3H2O (g) + N2 (g)
E) From dinitrogen (i) oxide: When dinitrogen (i) is passed over red-hot copper, the gas is reduced to nitrogen.
N2O (g) + CU(s) CUO(s) + N2 (g)
INDUSTRIAL PRPEARATION OF NITROGEN
Nitrogen is industrially prepared by the fractional distillation of liquid air. Carbon (iv) oxide is removed from air and such air is liquefied by successive compression and cooling processes. Upon distillation, nitrogen gas is given off first at -1960C (at S.P) and is separated from oxygen which boils at -1830C (at S.P). The nitrogen is stored in steel cylinders and sold as liquid nitrogen or as the compressed gas.
EVALUATION:
1. Explain the occurrence of nitrogen in the Free State and in the combined form.
2. Explain the laboratory preparation of nitrogen from air.
3. Explain the industrial preparation of nitrogen.
ASSIGNMENT:
1. What is an aspirator bottle used for?
2. Balance the equation below:
NH3 (g) + CuO(s) Cu(s) + H2O (g) + N2 (g)
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. List the physical properties of nitrogen
b. Explain the chemical properties of nitrogen with the aid of chemical equations.
c. List the uses of nitrogen.
CONTENT: PHYSICAL PROPERTIES OF NITROGEN
1. Nitrogen is a colourless, odourless and tasteless gas.
2. Pure nitrogen is slightly lighter than air.
3. It is only slightly soluble in water. Two volumes of the gas dissolved in 100 volumes of water at room temperature.
4. The melting point of nitrogen is -2100C and its boiling point is -1960C. These low temperatures are due to the weal Vander Waals forces which exist between the nitrogen molecules in the solid and liquid states.
CHEMICAL PROPERTIES OF NITROGEN
Nitrogen occurs in Group V of the periodic table and it has five valence electrons. It can exist in oxidation states of -3 to +5 in its compounds. Nitrogen gas exists in air as a diatomic molecule with triple covalent bonds between its atoms.
Oxidation states of Nitrogen in its compounds.
NAME OF COMPOUND FORMULA OXIDATION STATE
AMMONIA NH3 -3
HYDRAZINE N2H4 -2
HYDROXYLAMINE NH2OH -1
NITROGEN N2 0
DINITROGEN(I) OXIDE N2O +1
NITROGEN (II) OXIDE NO +2
DINITROGEN (III) OXIDE N2O3 +3
DIOXONITRATE(III) NO2- +3
NITROGEN (IV) OXIDE NO2 +4
DINITROGEN (V) OXIDE N2O5 +5
TRIOXONITRATE (V) NO3- +5
At very high temperature and pressures, nitrogen combines directly with hydrogen, oxygen and certain metals.
(1) With metals: nitrogen combines directly with very electropositive metals, e.g. magnesium, calcium, aluminum and iron to form nitrides.
3Mg(s) + N2(g) Mg3N2(g)
(Re d hot)
The nitride is readily hydrolyzed when warm with water to give ammonia gas.
Mg3N2(s) + 6H2O (l) 3Mg (OH) 2(s) + 2NH3 (g)
(2) With non-metals: Nitrogen combines with hydrogen to form NH3
N2 (g) + 3H2 (g) 2NH3 (g)
Nitrogen also combines directly with oxygen at very high temperatures (about 20000C) or in the presence of a high voltage electric spark to form small amounts of NO. in nature, this reaction occurs in the atmosphere when lightning flashes.
N2 (g) + O2 (g) 2NO (g)
USES OF NITROGEN
1. Nitrogen is used in the industrial manufacture of ammonia, cyanide, cyanamide and carbamide (a important fertilizer).
2. Liquid nitrogen is used as a cooling agent
3. Nitrogen has an inert nature and is thus used
(a) As a carrier gas in gas chromatography.
(b) In providing an inert atmosphere for certain industrial processes involving easily oxidizable chemicals,e.g. in making electronic components such as transistors, and in the annealing of metals;
(c) As a preservative to prevent rancidity (due to the oxidation of fats) in packaged foods.
EVALUATION:
1. List four physical properties of nitrogen.
2. Use chemical equation to explain the reaction of nitrogen with magnesium.
3. Write the equation for the reaction of nitrogen with oxygen.
ASSIGNMENT:
1. Determine the oxidation numbers of nitrogen in
(a) N2O5
(b) NH2OH
(c) N2O and hence give their IUPAC nomenclatures.
2. Explain what is meant by the annealing of metals and the use of nitrogen gas in this process.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to :
a. Explain the nature of ammonia
b. Explain the laboratory preparation of ammonia with the aid of a diagram.
CONTENT: AMMONIA (NH3)
Ammonia is a hydride of nitrogen. Natural ammonia is produced by the decomposition or decay of nitrogenous matter in the absence of air. The decomposition may be brought about by heat or putrefying bacteria. Thus, small traces of ammonia may be present in the air. But because of its great solubility in water, it rapidly dissolves in rain water and finds its way into the soil where it may be converted into other compounds.
LABORATORY PREPARATION OF AMMONIA
Ammonia is prepared in the laboratory by heating any ammonium salt with a non-volatile base [e.g. Ca (OH)2]
2NH4Cl(s) + Ca (OH)2(s) CaCl2(s) + 2H2O(l) + 2NH3(g)
Ca (OH)2 is preferred because it is cheap and not deliquescent like the caustic alkalis (KOH and NaOH). Both reactants [NH4Cl and Ca (OH)2] are solids and should be thoroughly ground to provide the maximum surface area for reaction.
The common drying agents like conc. H2SO4 and fused CaCl2 are not suitable for drying ammonia because they react with the gas as shown below:
2NH3 (g) + H2SO4(aq) (NH4)2SO4(s)
4NH3(g) + CaCl2(s) CaCl2.4NH3(s)
The preferred drying agent for ammonia gas is calcium oxide, CaO, (Quicklime) because it does not react with ammonia.
EVALUATION:
1. Explain how NH3 is produced naturally.
2. Explain the laboratory preparation of NH3.
3. Why are conc. H2SO4 and fused CaCl2
ASSIGNMENT:
1. Write the balanced chemical equation for the reaction between NH4Cl and Ca (OH)2.
2. Explain why it is necessary to dry the ammonia gas produced in the laboratory.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. Explain Haber process for the industrial manufacture of NH3 gas.
b. List the conditions necessary for maximum yield of NH3 gas.
c. Draw the diagram showing the industrial preparation of ammonia by the Haber process.
CONTENT: INDUSTRIAL PREPARATION OF AMMONIA (HABER PROCESS)
HABER PROCESS is used to manufacture ammonia from nitrogen and hydrogen gas. Since the direct combination between nitrogen and hydrogen is reversible, special conditions of reaction are necessary for the optimum yield of ammonia.
Special conditions of Reaction for the optimum Yield of Ammonia (Haber Process)
1. The Haber process involves mixing nitrogen and hydrogen in the volume ratio of 1:3 and passing the mixture
2. Over finely divided iron catalyst,
3. At a temperature of about 4500C, and
4. A pressure of about 200 atmospheres.
The yield of ammonia is about 15% under these conditions. The ammonia is then liquefied by cooling and the unused gases are re-circulated over the catalyst for further production of ammonia.
N2 (g) + 3H2 (g) 2NH3 (g) + heat
EVALUATION:
1. Explain the four conditions necessary for the optimum yield of ammonia using the Haber process.
2. Draw the Haber process chart for the industrial production of ammonia.
ASSIGNMENT:
1. State Le Chatelier's principle
2. Explain the effect of decrease in pressure on the equilibrium position in the Haber process for ammonia production.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the occurrence of nitrogen.
b. Describe the laboratory preparation of nitrogen with the aid of chemical equations and diagrams.
c. Explain the industrial preparation of nitrogen.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: OCCURRENCE OF NITROGEN
Nitrogen occurs chiefly in the free form in air, making up about 78% by volume of the atmosphere. Free nitrogen in air is important because it dilutes the oxygen to the point where combustion, respiration and oxidation of metals are reasonably slow. In the combined form, nitrogen occurs as trioxonitrates(v) of sodium and calcium, as well as ammonium salts (in the earth's crust) combined nitrogen is also found in organic matter such as proteins, urea and vitamin B compounds.
LABORATORY PREPARATION OF NITROGEN
A) From air:
Nitrogen is obtained from air by removing other constituents. CO2 and O2 are removed by passing air through caustic soda and heated copper turnings respectively. But, the nitrogen obtained this way is denser than pure nitrogen because it contains about 1% by volume of noble gases as impurities.
Nitrogen can also be prepared by the following chemical methods:
B) From ammonium dioxonitrate (iii)
NaNO2(aq) + NH4Cl(aq) NH4NO2(aq) + NaCl(aq)
NH4NO2(aq) 2H2O(l) + N2(g)
C) From ammonium heptaoxodichromate (vi)
(NH4)2Cr2O7(s) Cr2O3(s) + 4H2O (l) + N2 (g)
D) From ammonia: Nitrogen is liberated when ammonia is oxidized by hot copper (ii) oxide
2NH3 (g) + 3CUO(s) 3CU(s) + 3H2O (g) + N2 (g)
E) From dinitrogen (i) oxide: When dinitrogen (i) is passed over red-hot copper, the gas is reduced to nitrogen.
N2O (g) + CU(s) CUO(s) + N2 (g)
INDUSTRIAL PRPEARATION OF NITROGEN
Nitrogen is industrially prepared by the fractional distillation of liquid air. Carbon (iv) oxide is removed from air and such air is liquefied by successive compression and cooling processes. Upon distillation, nitrogen gas is given off first at -1960C (at S.P) and is separated from oxygen which boils at -1830C (at S.P). The nitrogen is stored in steel cylinders and sold as liquid nitrogen or as the compressed gas.
EVALUATION:
1. Explain the occurrence of nitrogen in the Free State and in the combined form.
2. Explain the laboratory preparation of nitrogen from air.
3. Explain the industrial preparation of nitrogen.
ASSIGNMENT:
1. What is an aspirator bottle used for?
2. Balance the equation below:
NH3 (g) + CuO(s) Cu(s) + H2O (g) + N2 (g)
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. List the physical properties of nitrogen
b. Explain the chemical properties of nitrogen with the aid of chemical equations.
c. List the uses of nitrogen.
CONTENT: PHYSICAL PROPERTIES OF NITROGEN
1. Nitrogen is a colourless, odourless and tasteless gas.
2. Pure nitrogen is slightly lighter than air.
3. It is only slightly soluble in water. Two volumes of the gas dissolved in 100 volumes of water at room temperature.
4. The melting point of nitrogen is -2100C and its boiling point is -1960C. These low temperatures are due to the weal Vander Waals forces which exist between the nitrogen molecules in the solid and liquid states.
CHEMICAL PROPERTIES OF NITROGEN
Nitrogen occurs in Group V of the periodic table and it has five valence electrons. It can exist in oxidation states of -3 to +5 in its compounds. Nitrogen gas exists in air as a diatomic molecule with triple covalent bonds between its atoms.
Oxidation states of Nitrogen in its compounds.
NAME OF COMPOUND FORMULA OXIDATION STATE
AMMONIA NH3 -3
HYDRAZINE N2H4 -2
HYDROXYLAMINE NH2OH -1
NITROGEN N2 0
DINITROGEN(I) OXIDE N2O +1
NITROGEN (II) OXIDE NO +2
DINITROGEN (III) OXIDE N2O3 +3
DIOXONITRATE(III) NO2- +3
NITROGEN (IV) OXIDE NO2 +4
DINITROGEN (V) OXIDE N2O5 +5
TRIOXONITRATE (V) NO3- +5
At very high temperature and pressures, nitrogen combines directly with hydrogen, oxygen and certain metals.
(1) With metals: nitrogen combines directly with very electropositive metals, e.g. magnesium, calcium, aluminum and iron to form nitrides.
3Mg(s) + N2(g) Mg3N2(g)
(Re d hot)
The nitride is readily hydrolyzed when warm with water to give ammonia gas.
Mg3N2(s) + 6H2O (l) 3Mg (OH) 2(s) + 2NH3 (g)
(2) With non-metals: Nitrogen combines with hydrogen to form NH3
N2 (g) + 3H2 (g) 2NH3 (g)
Nitrogen also combines directly with oxygen at very high temperatures (about 20000C) or in the presence of a high voltage electric spark to form small amounts of NO. in nature, this reaction occurs in the atmosphere when lightning flashes.
N2 (g) + O2 (g) 2NO (g)
USES OF NITROGEN
1. Nitrogen is used in the industrial manufacture of ammonia, cyanide, cyanamide and carbamide (a important fertilizer).
2. Liquid nitrogen is used as a cooling agent
3. Nitrogen has an inert nature and is thus used
(a) As a carrier gas in gas chromatography.
(b) In providing an inert atmosphere for certain industrial processes involving easily oxidizable chemicals,e.g. in making electronic components such as transistors, and in the annealing of metals;
(c) As a preservative to prevent rancidity (due to the oxidation of fats) in packaged foods.
EVALUATION:
1. List four physical properties of nitrogen.
2. Use chemical equation to explain the reaction of nitrogen with magnesium.
3. Write the equation for the reaction of nitrogen with oxygen.
ASSIGNMENT:
1. Determine the oxidation numbers of nitrogen in
(a) N2O5
(b) NH2OH
(c) N2O and hence give their IUPAC nomenclatures.
2. Explain what is meant by the annealing of metals and the use of nitrogen gas in this process.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to :
a. Explain the nature of ammonia
b. Explain the laboratory preparation of ammonia with the aid of a diagram.
CONTENT: AMMONIA (NH3)
Ammonia is a hydride of nitrogen. Natural ammonia is produced by the decomposition or decay of nitrogenous matter in the absence of air. The decomposition may be brought about by heat or putrefying bacteria. Thus, small traces of ammonia may be present in the air. But because of its great solubility in water, it rapidly dissolves in rain water and finds its way into the soil where it may be converted into other compounds.
LABORATORY PREPARATION OF AMMONIA
Ammonia is prepared in the laboratory by heating any ammonium salt with a non-volatile base [e.g. Ca (OH)2]
2NH4Cl(s) + Ca (OH)2(s) CaCl2(s) + 2H2O(l) + 2NH3(g)
Ca (OH)2 is preferred because it is cheap and not deliquescent like the caustic alkalis (KOH and NaOH). Both reactants [NH4Cl and Ca (OH)2] are solids and should be thoroughly ground to provide the maximum surface area for reaction.
The common drying agents like conc. H2SO4 and fused CaCl2 are not suitable for drying ammonia because they react with the gas as shown below:
2NH3 (g) + H2SO4(aq) (NH4)2SO4(s)
4NH3(g) + CaCl2(s) CaCl2.4NH3(s)
The preferred drying agent for ammonia gas is calcium oxide, CaO, (Quicklime) because it does not react with ammonia.
EVALUATION:
1. Explain how NH3 is produced naturally.
2. Explain the laboratory preparation of NH3.
3. Why are conc. H2SO4 and fused CaCl2
ASSIGNMENT:
1. Write the balanced chemical equation for the reaction between NH4Cl and Ca (OH)2.
2. Explain why it is necessary to dry the ammonia gas produced in the laboratory.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. Explain Haber process for the industrial manufacture of NH3 gas.
b. List the conditions necessary for maximum yield of NH3 gas.
c. Draw the diagram showing the industrial preparation of ammonia by the Haber process.
CONTENT: INDUSTRIAL PREPARATION OF AMMONIA (HABER PROCESS)
HABER PROCESS is used to manufacture ammonia from nitrogen and hydrogen gas. Since the direct combination between nitrogen and hydrogen is reversible, special conditions of reaction are necessary for the optimum yield of ammonia.
Special conditions of Reaction for the optimum Yield of Ammonia (Haber Process)
1. The Haber process involves mixing nitrogen and hydrogen in the volume ratio of 1:3 and passing the mixture
2. Over finely divided iron catalyst,
3. At a temperature of about 4500C, and
4. A pressure of about 200 atmospheres.
The yield of ammonia is about 15% under these conditions. The ammonia is then liquefied by cooling and the unused gases are re-circulated over the catalyst for further production of ammonia.
N2 (g) + 3H2 (g) 2NH3 (g) + heat
EVALUATION:
1. Explain the four conditions necessary for the optimum yield of ammonia using the Haber process.
2. Draw the Haber process chart for the industrial production of ammonia.
ASSIGNMENT:
1. State Le Chatelier's principle
2. Explain the effect of decrease in pressure on the equilibrium position in the Haber process for ammonia production.
WEEK 6
TOPIC: COMPOUNDS OF NITROGEN (AMMONIA)
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Draw and explain the structure of the ammonia ion starting with ammonia and hydrogen ion.
b. List the physical properties of ammonia.
c. Explain the chemical properties of ammonia
d. Describe the tests for ammonia.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: STRUCTURE OF AMMONIA AND AMMONIUM ION
In an ammonium molecule, there are three single covalent bonds between the nitrogen atom and hydrogen atoms (N - H) and a pair of lone electrons which is available for the formation of ammonium ion (NH4+) by coordinate covalent bonding or dative bonding.
PHYSICAL PROPERTIES OF AMMONIA
1. Ammonia is a colourless gas with a characteristic choking smell.
2. H3 in large quantities is poisonous because of its effect on the respiratory muscles.
3. It is an alkaline gas which changes moist red litmus paper to blue.
4. It is less dense than air.
5. It is highly soluble in water (as demonstrated by the fountain experiment) due to its readiness of forming hydrogen bonds with water to give aqueous ammonia, i.e. ammonium hydroxide, (which on warming decomposes to give ammonia gas;
NH4OH (aq) H2O (l) + NH3(g)
CHEMICAL PROPERTIES OF AMMONIUM
1. As a base e.g. NH3 + HCl NH4Cl
NH3 + HNO3 NH4NO3
2. As a reducing agent:
2NH3 + 3CUO 3CU + N2 + 3H2O
3. Reaction with oxygen:
4NH3 + 3O2 6H2O + 2N2
4. It forms urea with CO2
2NH3 + CO2 (NH2)2CO + H2O
5. It is a precipitating agent
Zn2+ (aq) + 2OH-(aq) Zn(OH)2(s)
TESTS FOR AMMONIA
Ammonia has an easily recognizable characteristic choking smell. Its presence can be confirmed by the following test.
a. Action on litmus paper: Hold a moist red litmus paper into the jar of the unknown gas. If the litmus paper turns blue, then the gas is probably ammonia as it is the only common alkaline gas.
b. Action with conc. HCl: Insert a piece of glass rod into conc. HCl and put it in a jar of the gas; dense white fumes are formed if the gas is ammonia.
NH3(g) + HCl(conc.) NH4Cl(g)(dense white fumes)
EVALUATION:
1. Draw the structure of ammonia showing the bonds and also show structurally how ammonia forms ammonium ions.
2. List the physical properties of ammonia.
3. Explain the chemical properties of ammonia with the aid of balanced chemical equations.
4. Give two tests for ammonia gas.
ASSIGNMENT:
1. Why is it necessary to moisten a piece of litmus paper when testing for the acidity or alkalinity of a gas?
2. What causes the dense white fumes formed when ammonia and conc. HCl come into contact?
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
1. List and explain the uses of ammonia.
2. Explain the nature of ammonium compounds (ammonium salts)
3. Explain the preparation of ammonia
4. List and explain the properties of ammonium salts with the aid of equations where necessary.
CONTENT: USES OF AMMONIA
1. For softening temporarily hard water.
2. Used in laundries as a cleansing agent- solvent for removing grease and oil stains.
3. Liquid ammonia is used as a refrigerant, although it is now being replaced by less toxic and unreactive fluorocarbons.
4. Ammonia is used in the manufacture of important compounds such as HNO3 and Na2CO3 by the solvate process.
5. The most important use of ammonia is in the manufacture of nitrogenous fertilizers like
a. (NH4)2SO4
b. NH4NO3
c. Carbamide and
d. (NH4)3PO4
COMPOUNDS OF AMMONIA (AMMONIUM SALTS)
Ammonium salts are electrovalent compounds which contain the ammonium ion, NH4+, as the cat ion.
Preparation: Ammonium salts are prepared by dissolving ammonia in the appropriate acid or neutralizing aqueous ammonia with the appropriate acid. The ammonium salts are then separated out of solution by crystallization and not by evaporation because they are easily decomposed by dry heating.
NH3(g) +HCl(aq) NH4Cl(aq)
NH4+(aq) + OH-(aq) + HCl(aq) NH4Cl(aq) + H2O(l)
NH3(g) + HNO3(aq) NH4NO3(aq)
NH4+(aq) + OH-(aq) + HNO3(aq) NH4NO3(aq) + H2O(l)
PROPERTIES OF AMMONIUM SALTS:
1. Appearance and solubility: All common ammonium salts are white crystalline solids which readily dissolve in water. They are completely ionized in solution and are strong electrolytes.
2. Action of heat:
(a) All ammonium salts decompose when heated e.g.
(NH4)2SO4(s) 2NH3(g) + H2SO4(l)
NH4NO3(s) N2O(g) + 2H2O(g)
NH4NO2(s) N2(g) + 2H2O(g)
(NH4)2CO3(s) 2NH3(g) + CO2(g) + H2O(g)
(b) Certain ammonium salts (e.g. NH4Cl) , however, sublime when heated e.g.
Heat
NH4Cl(s) NH3(g) + HCl(g)
Cold
3. Reaction with bases: All ammonium salts liberate ammonia when heated with bases and alkalis. This reaction is used in the laboratory preparation of ammonia. It also helps to distinguish between ammonium salts from normal metal salts.
NH4+(s) + OH-(aq) NH3(g) + H2O(l)
NH4NO3(s) + NaOH(aq) NaNO3(s) + NH3(g) + H2O(l)
EVALUATION:
1. Explain the nature of ammonium salts in terms of chemical bonding.
2. List the uses of ammonia
3. Explain the general method of preparing ammonium salts.
4. Briefly describe the action of heat on ammonium salts.
ASSIGNMENT:
1. What is sublimation?
2. Name the types of ammonium salt which sublimes and represent this with the aid of a balanced chemical equation.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. Test for ammonium salts
b. List some important ammonium salt and their uses.
c. List the oxides of nitrogen and describe their preparation
CONTENT: TEST FOR AMMONIUM SALTS
Heat some of the unknown substance with sodium hydroxide solution. Note the smell of any gas that is given off and test it with a moist red litmus paper. If the unknown substance is an ammonium salt, ammonia gas will be evolved, and this can be identified by its characteristic choking smell and action on moist red litmus paper which turns blue.
NH4(s)+NaOH(aq) Na+(aq) + H2O(l) + NH3(g)
NH4Cl(s) + NaOH(aq) NaCl(aq) + H2O(l) + NH3(aq)
SOME IMPORTANT AMMONIUM SALTS:
1. NH4Cl, ammonium chloride is used in Leclanche and dry cells. It is also used as a flux to increase the fusibility of solders and as an analytical reagent in the laboratory.
2. Ammonium tetraoxosulphate (VI), (NH4)2SO4 is used as a fertilizer and in a more concentrated form as a weed killer.
3. Ammonium trioxonitrate (V), NH4NO3 is used as a fertilizer e.g. nitrochalk and in making explosives e.g. amated or ammonal. A liquid of very low temperature can be obtained by dissolving a large quantity of the trioxonitrate (V) in water and this can be used as a freezing mixture.
4. Ammonium trioxocarbonate (IV) is used as an analytical reagent in the laboratory. It decomposes slightly even at room temperature to liberate ammonia and so is commonly used in smelling salts to prevent dizziness and fainting.
OXIDES OF NITROGEN
Nitrogen forms varieties of oxides with oxygen. Some of these are N2O (Neutral oxide), NO, NO2 (acidic oxide) N2O4 etc.
PREPARATION OF OXIDES OF NITROGEN:
They are prepared by decomposition of nitrogen compounds e.g.
NH4NO3 2H2O + N2O
2Pb(NO3)2 PbO + 4NO2 + O2
EVALUATION:
1. Explain the test for ammonium salts.
2. List four important ammonium salts and their uses
3. List four oxides of nitrogen and explain their general method of preparation.
ASSIGNMENT:
1. Define a neutral oxide and give an example of a neutral oxide that is an oxide of nitrogen.
2. Define an acidic oxide with an example of an oxide of nitrogen that is acidic oxide.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
1. Explain the laboratory and industrial preparations of trioxonitrate (V) acid, HNO3
2. List and explain the physical and chemical properties of HNO3.
3. List the uses of HNO3
4. Give the test for NO3- (Brown ring test)
CONTENT: TRIOXONITRATE (V) ACID, HNO3
Laboratory preparation: By displacing it from any trioxonitrate (V) using concentrated H2SO4 which is a less volatile acid. The ttrioxonitrates (V) of potassium and sodium are usually used because they are cheap.
KNO3(s) + H2SO4(aq) KHSO4(aq) + HNO3(g)
NaNO3(s) + H2SO4(aq) NaHSO4(aq) + HNO3(g)
INDUSTRIAL PREPARATION: HNO3 is prepared on a large scale industrially by catalytic oxidation of ammonia. The process is divided into three stages.
1. Oxidation of ammonia to NO using platinum - rhodium catalyst at about 7000C.
4NH3 + 5O2 4NO + 6H2O
2. Mixing of No with excess air to produce NO2 i.e. 2NO + O2 2NO2
3. Passing of hot water in the presence of excess air to produce 50% concentrated HNO3 i.e
4NO2 + 2H2O + O2 4HNO3
PHYSICAL PROPERTIES OF HNO3
1. HNO3 is fuming liquid with a sharp choking smell.
2. Although it is colourless when pure, it tends to turn yellowish after some time due to the decomposition of some of the acid to yield NO2, which then dissolves in it.
3. Pure HNO3 is miscible with water.
4. The dilute acid turns blue litmus red.
5. The pure acid is very corrosive and readily destroys organic matter such as skin, rubber, cork and clothing. Even ordinary concentrated HNO3 must be handled with care.
CHEMICAL PROPERTIES OF HNO3
1. As an acid, its dilute form reacts with bases and trioxocarbonates (IV).
HNO3 + NaOH NaNO3 + H20
2. HNO3 acts as oxidizing agent e.g.
C + 4 HNO3 CO2 + 2H2O + 4NO2
3CU + 8HNO3 3CU (NO3)2 + 4 H20 + 2NO
3. Decomposition: The acid decompose slowly at room temperature and rapidly when heated to yield H2O, NO2 and O2, i.e.
4HNO3 2H2O + 4NO2 + O2
USES OF HNO3
1. As an oxidizing agent and a nitrating agent in the laboratory.
2. As a rocket fuel.
3. As an oxidizing agent in polymer synthesis like nylon and terylene.
4. For making some compounds like fertilizers, dyes etc.
5. For making explosives, drugs etc.
TEST FOR NO3- (BROWN RING TEST)
Add few drops of dil.H2SO4 to the aqueous solution, followed by freshly prepared FeSO4 solution and shake well. Tilt the test-tube and carefully pour few drops of conc.H2SO4, a brown ring formed at the junction of the concentrated acid and the solution confirms the presence of NO3-.
EVALUATION:
a. Explain how to prepare HNO3 in the laboratory and industrially.
b. List the physical properties of HNO3.
c. List the chemical properties of HNO3
d. List five uses of HNO3
e. Discuss the brown ring test for NO3-
ASSIGNMENT:
1. Write the chemical equation for the reaction between HNO3 and CaCO3.
2. Give an example of a reaction in which ammonia behaves as a (i) base and as a (ii) precipitating agent.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Draw and explain the structure of the ammonia ion starting with ammonia and hydrogen ion.
b. List the physical properties of ammonia.
c. Explain the chemical properties of ammonia
d. Describe the tests for ammonia.
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: STRUCTURE OF AMMONIA AND AMMONIUM ION
In an ammonium molecule, there are three single covalent bonds between the nitrogen atom and hydrogen atoms (N - H) and a pair of lone electrons which is available for the formation of ammonium ion (NH4+) by coordinate covalent bonding or dative bonding.
PHYSICAL PROPERTIES OF AMMONIA
1. Ammonia is a colourless gas with a characteristic choking smell.
2. H3 in large quantities is poisonous because of its effect on the respiratory muscles.
3. It is an alkaline gas which changes moist red litmus paper to blue.
4. It is less dense than air.
5. It is highly soluble in water (as demonstrated by the fountain experiment) due to its readiness of forming hydrogen bonds with water to give aqueous ammonia, i.e. ammonium hydroxide, (which on warming decomposes to give ammonia gas;
NH4OH (aq) H2O (l) + NH3(g)
CHEMICAL PROPERTIES OF AMMONIUM
1. As a base e.g. NH3 + HCl NH4Cl
NH3 + HNO3 NH4NO3
2. As a reducing agent:
2NH3 + 3CUO 3CU + N2 + 3H2O
3. Reaction with oxygen:
4NH3 + 3O2 6H2O + 2N2
4. It forms urea with CO2
2NH3 + CO2 (NH2)2CO + H2O
5. It is a precipitating agent
Zn2+ (aq) + 2OH-(aq) Zn(OH)2(s)
TESTS FOR AMMONIA
Ammonia has an easily recognizable characteristic choking smell. Its presence can be confirmed by the following test.
a. Action on litmus paper: Hold a moist red litmus paper into the jar of the unknown gas. If the litmus paper turns blue, then the gas is probably ammonia as it is the only common alkaline gas.
b. Action with conc. HCl: Insert a piece of glass rod into conc. HCl and put it in a jar of the gas; dense white fumes are formed if the gas is ammonia.
NH3(g) + HCl(conc.) NH4Cl(g)(dense white fumes)
EVALUATION:
1. Draw the structure of ammonia showing the bonds and also show structurally how ammonia forms ammonium ions.
2. List the physical properties of ammonia.
3. Explain the chemical properties of ammonia with the aid of balanced chemical equations.
4. Give two tests for ammonia gas.
ASSIGNMENT:
1. Why is it necessary to moisten a piece of litmus paper when testing for the acidity or alkalinity of a gas?
2. What causes the dense white fumes formed when ammonia and conc. HCl come into contact?
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
1. List and explain the uses of ammonia.
2. Explain the nature of ammonium compounds (ammonium salts)
3. Explain the preparation of ammonia
4. List and explain the properties of ammonium salts with the aid of equations where necessary.
CONTENT: USES OF AMMONIA
1. For softening temporarily hard water.
2. Used in laundries as a cleansing agent- solvent for removing grease and oil stains.
3. Liquid ammonia is used as a refrigerant, although it is now being replaced by less toxic and unreactive fluorocarbons.
4. Ammonia is used in the manufacture of important compounds such as HNO3 and Na2CO3 by the solvate process.
5. The most important use of ammonia is in the manufacture of nitrogenous fertilizers like
a. (NH4)2SO4
b. NH4NO3
c. Carbamide and
d. (NH4)3PO4
COMPOUNDS OF AMMONIA (AMMONIUM SALTS)
Ammonium salts are electrovalent compounds which contain the ammonium ion, NH4+, as the cat ion.
Preparation: Ammonium salts are prepared by dissolving ammonia in the appropriate acid or neutralizing aqueous ammonia with the appropriate acid. The ammonium salts are then separated out of solution by crystallization and not by evaporation because they are easily decomposed by dry heating.
NH3(g) +HCl(aq) NH4Cl(aq)
NH4+(aq) + OH-(aq) + HCl(aq) NH4Cl(aq) + H2O(l)
NH3(g) + HNO3(aq) NH4NO3(aq)
NH4+(aq) + OH-(aq) + HNO3(aq) NH4NO3(aq) + H2O(l)
PROPERTIES OF AMMONIUM SALTS:
1. Appearance and solubility: All common ammonium salts are white crystalline solids which readily dissolve in water. They are completely ionized in solution and are strong electrolytes.
2. Action of heat:
(a) All ammonium salts decompose when heated e.g.
(NH4)2SO4(s) 2NH3(g) + H2SO4(l)
NH4NO3(s) N2O(g) + 2H2O(g)
NH4NO2(s) N2(g) + 2H2O(g)
(NH4)2CO3(s) 2NH3(g) + CO2(g) + H2O(g)
(b) Certain ammonium salts (e.g. NH4Cl) , however, sublime when heated e.g.
Heat
NH4Cl(s) NH3(g) + HCl(g)
Cold
3. Reaction with bases: All ammonium salts liberate ammonia when heated with bases and alkalis. This reaction is used in the laboratory preparation of ammonia. It also helps to distinguish between ammonium salts from normal metal salts.
NH4+(s) + OH-(aq) NH3(g) + H2O(l)
NH4NO3(s) + NaOH(aq) NaNO3(s) + NH3(g) + H2O(l)
EVALUATION:
1. Explain the nature of ammonium salts in terms of chemical bonding.
2. List the uses of ammonia
3. Explain the general method of preparing ammonium salts.
4. Briefly describe the action of heat on ammonium salts.
ASSIGNMENT:
1. What is sublimation?
2. Name the types of ammonium salt which sublimes and represent this with the aid of a balanced chemical equation.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
a. Test for ammonium salts
b. List some important ammonium salt and their uses.
c. List the oxides of nitrogen and describe their preparation
CONTENT: TEST FOR AMMONIUM SALTS
Heat some of the unknown substance with sodium hydroxide solution. Note the smell of any gas that is given off and test it with a moist red litmus paper. If the unknown substance is an ammonium salt, ammonia gas will be evolved, and this can be identified by its characteristic choking smell and action on moist red litmus paper which turns blue.
NH4(s)+NaOH(aq) Na+(aq) + H2O(l) + NH3(g)
NH4Cl(s) + NaOH(aq) NaCl(aq) + H2O(l) + NH3(aq)
SOME IMPORTANT AMMONIUM SALTS:
1. NH4Cl, ammonium chloride is used in Leclanche and dry cells. It is also used as a flux to increase the fusibility of solders and as an analytical reagent in the laboratory.
2. Ammonium tetraoxosulphate (VI), (NH4)2SO4 is used as a fertilizer and in a more concentrated form as a weed killer.
3. Ammonium trioxonitrate (V), NH4NO3 is used as a fertilizer e.g. nitrochalk and in making explosives e.g. amated or ammonal. A liquid of very low temperature can be obtained by dissolving a large quantity of the trioxonitrate (V) in water and this can be used as a freezing mixture.
4. Ammonium trioxocarbonate (IV) is used as an analytical reagent in the laboratory. It decomposes slightly even at room temperature to liberate ammonia and so is commonly used in smelling salts to prevent dizziness and fainting.
OXIDES OF NITROGEN
Nitrogen forms varieties of oxides with oxygen. Some of these are N2O (Neutral oxide), NO, NO2 (acidic oxide) N2O4 etc.
PREPARATION OF OXIDES OF NITROGEN:
They are prepared by decomposition of nitrogen compounds e.g.
NH4NO3 2H2O + N2O
2Pb(NO3)2 PbO + 4NO2 + O2
EVALUATION:
1. Explain the test for ammonium salts.
2. List four important ammonium salts and their uses
3. List four oxides of nitrogen and explain their general method of preparation.
ASSIGNMENT:
1. Define a neutral oxide and give an example of a neutral oxide that is an oxide of nitrogen.
2. Define an acidic oxide with an example of an oxide of nitrogen that is acidic oxide.
BEHAVIOURAL OBJECTIVE: At the end of the lesson, the students should be able to:
1. Explain the laboratory and industrial preparations of trioxonitrate (V) acid, HNO3
2. List and explain the physical and chemical properties of HNO3.
3. List the uses of HNO3
4. Give the test for NO3- (Brown ring test)
CONTENT: TRIOXONITRATE (V) ACID, HNO3
Laboratory preparation: By displacing it from any trioxonitrate (V) using concentrated H2SO4 which is a less volatile acid. The ttrioxonitrates (V) of potassium and sodium are usually used because they are cheap.
KNO3(s) + H2SO4(aq) KHSO4(aq) + HNO3(g)
NaNO3(s) + H2SO4(aq) NaHSO4(aq) + HNO3(g)
INDUSTRIAL PREPARATION: HNO3 is prepared on a large scale industrially by catalytic oxidation of ammonia. The process is divided into three stages.
1. Oxidation of ammonia to NO using platinum - rhodium catalyst at about 7000C.
4NH3 + 5O2 4NO + 6H2O
2. Mixing of No with excess air to produce NO2 i.e. 2NO + O2 2NO2
3. Passing of hot water in the presence of excess air to produce 50% concentrated HNO3 i.e
4NO2 + 2H2O + O2 4HNO3
PHYSICAL PROPERTIES OF HNO3
1. HNO3 is fuming liquid with a sharp choking smell.
2. Although it is colourless when pure, it tends to turn yellowish after some time due to the decomposition of some of the acid to yield NO2, which then dissolves in it.
3. Pure HNO3 is miscible with water.
4. The dilute acid turns blue litmus red.
5. The pure acid is very corrosive and readily destroys organic matter such as skin, rubber, cork and clothing. Even ordinary concentrated HNO3 must be handled with care.
CHEMICAL PROPERTIES OF HNO3
1. As an acid, its dilute form reacts with bases and trioxocarbonates (IV).
HNO3 + NaOH NaNO3 + H20
2. HNO3 acts as oxidizing agent e.g.
C + 4 HNO3 CO2 + 2H2O + 4NO2
3CU + 8HNO3 3CU (NO3)2 + 4 H20 + 2NO
3. Decomposition: The acid decompose slowly at room temperature and rapidly when heated to yield H2O, NO2 and O2, i.e.
4HNO3 2H2O + 4NO2 + O2
USES OF HNO3
1. As an oxidizing agent and a nitrating agent in the laboratory.
2. As a rocket fuel.
3. As an oxidizing agent in polymer synthesis like nylon and terylene.
4. For making some compounds like fertilizers, dyes etc.
5. For making explosives, drugs etc.
TEST FOR NO3- (BROWN RING TEST)
Add few drops of dil.H2SO4 to the aqueous solution, followed by freshly prepared FeSO4 solution and shake well. Tilt the test-tube and carefully pour few drops of conc.H2SO4, a brown ring formed at the junction of the concentrated acid and the solution confirms the presence of NO3-.
EVALUATION:
a. Explain how to prepare HNO3 in the laboratory and industrially.
b. List the physical properties of HNO3.
c. List the chemical properties of HNO3
d. List five uses of HNO3
e. Discuss the brown ring test for NO3-
ASSIGNMENT:
1. Write the chemical equation for the reaction between HNO3 and CaCO3.
2. Give an example of a reaction in which ammonia behaves as a (i) base and as a (ii) precipitating agent.
WEEK 7
TOPIC: SULPHUR AND ITS COMPOUNDS
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the occurrence of sulphur
b. Use the Frasch process to explain the extraction of sulphur.
c. List the allotropes of sulphur
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: SULPHUR
OCCURRENCE OF SULPUR: Sulphur has long since been known for its medicinal value and germicidal effect since 1000B.C. but, its chemical nature was discovered in 1787 when Lavoisier recognized it as an element.
Sulphur makes up about 0.1% of the earth’s crust. It occurs freely as deposits in U.S.A, Poland, Japan, New Zealand and in Sicily in Italy. Sulphur is widely found in the combined state as sulphides of Iron, Zinc, Lead, Copper and mercury, and as the tetraoxosulphate (VI) salts of calcium, magnesium and barium. Sulphur is also preset in some proteins.
EXTRACTION OF SULPHUR
Sulphur is extracted through the FRASCH PROCESS from underground deposits of sulphur which may be more than 200m below the surface of the earth.
ALLOTROPES OF SULPHUR
The main allotropes of sulphur are RHOMBIC SULPHUR (α – sulphur) and MONOCLINIC OR PRISMATIC SULPHUR ( β- sulphur) which are crystalline, and AMORPHOUS SULPHUR ( δ- sulphur). There is also another form called PLASTIC SULPHUR.
1) RHOMBIC SULPHUR (α – sulphur)
2) MONOCLINIC OR PRISMATIC ( β- sulphur)
3) AMORPHOUS SULPHUR ( δ- sulphur)
4) PLASTIC SULPHUR
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the important ancient uses of sulphur.
2. Draw and explain the Frasch process for extracting sulphur.
3. List the four allotropes of sulphur
ASSIGNMENT: Classify the allotropes of sulphur to:
(1) Crystalline
(2) Non-crystalline (Amorphous)
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the allotropes of sulphur ad classify them into crystalline and non-crystalline.
2. Give the differences between rhombic sulphur and monoclinic sulphur.
3. Explain transition temperature for two allotropes of sulphur.
4. Explain the nature of amorphous sulphur and plastic sulphur.
CONTENT: ALLOTROPES OF SULPHUR
DIFFERENCES BETWEEN RHOMBIC AND MONOCLINIC SULPHUR
S/N RHOMBIC (α – sulphur) MONOCLINIC ( β- sulphur)
1 Bright yellow colour Amber colour
2 Octahedral in shape Needle-like in shape
3 Density of about 2.08g/cm3 because the S8 molecules are more tightly packed Density of about 1.98g/cm3 because the S8 molecules are less tightly packed
4 Has a melting point of about 1130C Has a melting point of about 1190C
5 Only stable below 960C Stable between 960C and 1190C
Rhombic and monoclinic sulphur has the following relationship
Between 960C and 1190C
RHOMBIC SULPHUR MONOCLINIC SULPHUR
Below 960C
Rhombic sulphur and monoclinic sulphur change from one form to the other at 960C. This is known as the TRANSITION TEMPERATURE for the two allotropes.
TRANSITION TEMPERATURE for two allotropes of the same element is the temperature at which one allotrope changes into another allotrope; and this is at 960C for rhombic sulphur to change to monoclinic sulphur.
AMORPHOUS SULPHUR has no regular crystalline shape and it is prepared as a pale yellow, almost white deposit when H2S is bubbled through H2O for a long time and the saturated solution is exposed to air
2H2S(g) + O2(g) 2H2O(l) + 2S(s)
PLASTIC SULPHUR is a super cooled form of sulphur. It is prepared by heating yellow sulphur which is then poured into cold water, and it will roll up into yellow ribbons which resemble plastic material. Plastic sulphur is generally not considered to be a true allotrope of sulphur because it is unstable and reverts to rhombic sulphur on standing.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Give the four differences between rhombic sulphur and monoclinic sulphur.
2. Explain what is meant by the transition temperature of allotropes
3. Explain the nature of amorphous sulphur and plastic sulphur
ASSIGNMENT:
1. Explain how to prepare amorphous sulphur and plastic sulphur.
2. Define and show with the aid of equation, the transition temperature of sulphur allotropes.
3. Draw a chart of allotropes of sulphur based on their classification as crystalline and non-crystalline.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to :
a. List the physical properties of sulphur.
b. List and explain the chemical properties of sulphur.
CONTENT: PHYSICAL PROPERTIES OF SULPHUR
1. Sulphur is a yellow solid which exists in two forms- crystalline and amorphous.
2. It is insoluble in water but soluble in carbon (IV) sulphide and methyl benzene.
3. Sulphur is a non-metal and is thus a bad conductor of heat and electricity.
4. The density of sulphur depends on the allotropic form.
5. Sulphur has a melting point of 1190C and a boiling point of 4440C.
CHEMICAL PROPERTIES OF SULPHUR
Like oxygen, sulphur is in Group VI of the periodic table. Sulphur atom has six valence electrons like the oxygen atom.
[16S:K2L8M6; 8O: K2L6]. For sulphur to attain octet stability, it gains two electrons, usually from Groups I and I metals to form the divalent sulphide ion, S2-. With non-metals, sulphur attains the octet structure by sharing electrons to form covalent compounds such as hydrogen sulphide, H-S-H. Sulphur can have oxidation states ranging from -2 to +6.
TABLE OF THE OXIDATION STATES OF SULPHUR IN ITS COMPOUNDS
NAME OF COMPOUND FORMULA OXIDATION STATE
Tetraoxosulphate (V) acid H2SO4 +6
Sulphur (IV) oxide SO2 +4
Sulphur (VI) oxide SO3 +6
Sulphur S8 0
Hydrogen sulphide H2S -2
1. DIRECT COMBINATION OF SULPHUR WITH OTHER ELEMENTS:
Sulphur combines directly with nearly all metals and non metals.
a. With metals: Fe(s) + S(s) FeS(s)
2Cu(s) + S(s) Cu2S(s)
b. With oxygen: O2(g) + S(s) SO2(g)
c. With hydrogen: H2(g) + S(s) H2S(g)
d. With carbon: C(s) + 2S(g) CS2(l)
e. With other non-metals to form various sulphides e.g. tetraphosphorus trisulphide, P4S3; disulphide dichloride S2Cl2 and sulphur hexafluoride, SF6.
2. ACTION OF OXIDIZING ACIDS ON SULPHUR:
2H2SO4 (aq) + S(s) 2H2O(l) + 3SO2(g)
6HNO3(aq) + S(s) H2SO4(aq) + 6NO2(g) + 2H2O(l)
EVALUATION: The students should be able to :
1. List the physical properties of sulphur.
2. Explain how sulphur exhibits oxidation states of from -2 to + 6.
ASSIGNMENT:
Write the balanced chemical equations for the reaction between sulphur and
i. Iron
ii. Copper
iii. Oxygen
iv. Hydrogen
v. Carbon
PERIOD : 4
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to :
i. List the uses of sulphur
ii. Briefly explain the occurrence of hydrogen sulphide
iii. Explain the preparation of hydrogen sulphide, with the use of Kipp’s apparatus showing its diagram.
CONTENT: USES OF SULPHUR
1. Sulphur is used in the vulcanization of rubber.
2. Sulphur is used as a fungicide and an insecticide for spraying crops.
3. Sulphur is used in the manufacture of bleaching agent used in the pulp and paper industry.
4. Sulphur is used to produce SO2 for the manufacture of H2SO4.
5. It is also used for the production of carbon (IV) sulphide, skin ointments and dyes, and as sulphides in manufacturing matches, fireworks and gun powder.
HYDROGEN SULPHIDE (H2S)
OCCURRENCE: Hydrogen sulphide is found in volcanic gases, sulphur springs, coal gas and gases formed during the decay of organic matter containing sulphur.
PREPARATION OF H2S
H2S is prepared both in the laboratory and commercially by the action of a dilute acid on a metallic sulphide e.g.
2HCl(aq) + FeS(s) FeCl2(aq) + H2S(g)
H2SO4 (aq) + FeS(S) FeSO4 (aq) + H2S (g)
H2S gas is easily liquefied and may be purchased in this form in steel cylinders.
The Kipp’s apparatus is used to prepare H2S in the laboratory because of regular use.
KIPP’S APPARATUS: is used for the intermittent supply of a gas i.e. it allows a gas to be supplied any time it is needed.
EVALUATION: The students should be able to:
i. List four uses of sulphur.
ii. Explain the occurrence of sulphur.
iii. Use balanced chemical equations to explain the preparation of H2S.
iv. What is Kipp’s apparatus?
ASSIGNMENT:
i. Use Kipp’s apparatus diagram to show how H2S is prepared from a dilute acid and FeS.
ii. Explain the difference between the isotopes and allotropes of a given element.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain the occurrence of sulphur
b. Use the Frasch process to explain the extraction of sulphur.
c. List the allotropes of sulphur
REFERENCE: NEW SCHOOL CHEMISTRY by ABABIO; ESSENTIAL CHEMISTRY by O. ODESINA
CONTENT: SULPHUR
OCCURRENCE OF SULPUR: Sulphur has long since been known for its medicinal value and germicidal effect since 1000B.C. but, its chemical nature was discovered in 1787 when Lavoisier recognized it as an element.
Sulphur makes up about 0.1% of the earth’s crust. It occurs freely as deposits in U.S.A, Poland, Japan, New Zealand and in Sicily in Italy. Sulphur is widely found in the combined state as sulphides of Iron, Zinc, Lead, Copper and mercury, and as the tetraoxosulphate (VI) salts of calcium, magnesium and barium. Sulphur is also preset in some proteins.
EXTRACTION OF SULPHUR
Sulphur is extracted through the FRASCH PROCESS from underground deposits of sulphur which may be more than 200m below the surface of the earth.
ALLOTROPES OF SULPHUR
The main allotropes of sulphur are RHOMBIC SULPHUR (α – sulphur) and MONOCLINIC OR PRISMATIC SULPHUR ( β- sulphur) which are crystalline, and AMORPHOUS SULPHUR ( δ- sulphur). There is also another form called PLASTIC SULPHUR.
1) RHOMBIC SULPHUR (α – sulphur)
2) MONOCLINIC OR PRISMATIC ( β- sulphur)
3) AMORPHOUS SULPHUR ( δ- sulphur)
4) PLASTIC SULPHUR
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Explain the important ancient uses of sulphur.
2. Draw and explain the Frasch process for extracting sulphur.
3. List the four allotropes of sulphur
ASSIGNMENT: Classify the allotropes of sulphur to:
(1) Crystalline
(2) Non-crystalline (Amorphous)
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. List the allotropes of sulphur ad classify them into crystalline and non-crystalline.
2. Give the differences between rhombic sulphur and monoclinic sulphur.
3. Explain transition temperature for two allotropes of sulphur.
4. Explain the nature of amorphous sulphur and plastic sulphur.
CONTENT: ALLOTROPES OF SULPHUR
DIFFERENCES BETWEEN RHOMBIC AND MONOCLINIC SULPHUR
S/N RHOMBIC (α – sulphur) MONOCLINIC ( β- sulphur)
1 Bright yellow colour Amber colour
2 Octahedral in shape Needle-like in shape
3 Density of about 2.08g/cm3 because the S8 molecules are more tightly packed Density of about 1.98g/cm3 because the S8 molecules are less tightly packed
4 Has a melting point of about 1130C Has a melting point of about 1190C
5 Only stable below 960C Stable between 960C and 1190C
Rhombic and monoclinic sulphur has the following relationship
Between 960C and 1190C
RHOMBIC SULPHUR MONOCLINIC SULPHUR
Below 960C
Rhombic sulphur and monoclinic sulphur change from one form to the other at 960C. This is known as the TRANSITION TEMPERATURE for the two allotropes.
TRANSITION TEMPERATURE for two allotropes of the same element is the temperature at which one allotrope changes into another allotrope; and this is at 960C for rhombic sulphur to change to monoclinic sulphur.
AMORPHOUS SULPHUR has no regular crystalline shape and it is prepared as a pale yellow, almost white deposit when H2S is bubbled through H2O for a long time and the saturated solution is exposed to air
2H2S(g) + O2(g) 2H2O(l) + 2S(s)
PLASTIC SULPHUR is a super cooled form of sulphur. It is prepared by heating yellow sulphur which is then poured into cold water, and it will roll up into yellow ribbons which resemble plastic material. Plastic sulphur is generally not considered to be a true allotrope of sulphur because it is unstable and reverts to rhombic sulphur on standing.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Give the four differences between rhombic sulphur and monoclinic sulphur.
2. Explain what is meant by the transition temperature of allotropes
3. Explain the nature of amorphous sulphur and plastic sulphur
ASSIGNMENT:
1. Explain how to prepare amorphous sulphur and plastic sulphur.
2. Define and show with the aid of equation, the transition temperature of sulphur allotropes.
3. Draw a chart of allotropes of sulphur based on their classification as crystalline and non-crystalline.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to :
a. List the physical properties of sulphur.
b. List and explain the chemical properties of sulphur.
CONTENT: PHYSICAL PROPERTIES OF SULPHUR
1. Sulphur is a yellow solid which exists in two forms- crystalline and amorphous.
2. It is insoluble in water but soluble in carbon (IV) sulphide and methyl benzene.
3. Sulphur is a non-metal and is thus a bad conductor of heat and electricity.
4. The density of sulphur depends on the allotropic form.
5. Sulphur has a melting point of 1190C and a boiling point of 4440C.
CHEMICAL PROPERTIES OF SULPHUR
Like oxygen, sulphur is in Group VI of the periodic table. Sulphur atom has six valence electrons like the oxygen atom.
[16S:K2L8M6; 8O: K2L6]. For sulphur to attain octet stability, it gains two electrons, usually from Groups I and I metals to form the divalent sulphide ion, S2-. With non-metals, sulphur attains the octet structure by sharing electrons to form covalent compounds such as hydrogen sulphide, H-S-H. Sulphur can have oxidation states ranging from -2 to +6.
TABLE OF THE OXIDATION STATES OF SULPHUR IN ITS COMPOUNDS
NAME OF COMPOUND FORMULA OXIDATION STATE
Tetraoxosulphate (V) acid H2SO4 +6
Sulphur (IV) oxide SO2 +4
Sulphur (VI) oxide SO3 +6
Sulphur S8 0
Hydrogen sulphide H2S -2
1. DIRECT COMBINATION OF SULPHUR WITH OTHER ELEMENTS:
Sulphur combines directly with nearly all metals and non metals.
a. With metals: Fe(s) + S(s) FeS(s)
2Cu(s) + S(s) Cu2S(s)
b. With oxygen: O2(g) + S(s) SO2(g)
c. With hydrogen: H2(g) + S(s) H2S(g)
d. With carbon: C(s) + 2S(g) CS2(l)
e. With other non-metals to form various sulphides e.g. tetraphosphorus trisulphide, P4S3; disulphide dichloride S2Cl2 and sulphur hexafluoride, SF6.
2. ACTION OF OXIDIZING ACIDS ON SULPHUR:
2H2SO4 (aq) + S(s) 2H2O(l) + 3SO2(g)
6HNO3(aq) + S(s) H2SO4(aq) + 6NO2(g) + 2H2O(l)
EVALUATION: The students should be able to :
1. List the physical properties of sulphur.
2. Explain how sulphur exhibits oxidation states of from -2 to + 6.
ASSIGNMENT:
Write the balanced chemical equations for the reaction between sulphur and
i. Iron
ii. Copper
iii. Oxygen
iv. Hydrogen
v. Carbon
PERIOD : 4
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to :
i. List the uses of sulphur
ii. Briefly explain the occurrence of hydrogen sulphide
iii. Explain the preparation of hydrogen sulphide, with the use of Kipp’s apparatus showing its diagram.
CONTENT: USES OF SULPHUR
1. Sulphur is used in the vulcanization of rubber.
2. Sulphur is used as a fungicide and an insecticide for spraying crops.
3. Sulphur is used in the manufacture of bleaching agent used in the pulp and paper industry.
4. Sulphur is used to produce SO2 for the manufacture of H2SO4.
5. It is also used for the production of carbon (IV) sulphide, skin ointments and dyes, and as sulphides in manufacturing matches, fireworks and gun powder.
HYDROGEN SULPHIDE (H2S)
OCCURRENCE: Hydrogen sulphide is found in volcanic gases, sulphur springs, coal gas and gases formed during the decay of organic matter containing sulphur.
PREPARATION OF H2S
H2S is prepared both in the laboratory and commercially by the action of a dilute acid on a metallic sulphide e.g.
2HCl(aq) + FeS(s) FeCl2(aq) + H2S(g)
H2SO4 (aq) + FeS(S) FeSO4 (aq) + H2S (g)
H2S gas is easily liquefied and may be purchased in this form in steel cylinders.
The Kipp’s apparatus is used to prepare H2S in the laboratory because of regular use.
KIPP’S APPARATUS: is used for the intermittent supply of a gas i.e. it allows a gas to be supplied any time it is needed.
EVALUATION: The students should be able to:
i. List four uses of sulphur.
ii. Explain the occurrence of sulphur.
iii. Use balanced chemical equations to explain the preparation of H2S.
iv. What is Kipp’s apparatus?
ASSIGNMENT:
i. Use Kipp’s apparatus diagram to show how H2S is prepared from a dilute acid and FeS.
ii. Explain the difference between the isotopes and allotropes of a given element.
WEEK 8
TOPIC: SULPHUR AND ITS COMPOUNDS
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List the physical properties of H2S.
b. Explain the chemical properties of H2S.
c. Give the test for H2S.
CONTENT: PHYSICAL PROPERTIES OF HYDROGEN SULPHIDE (H2S)
1. H2S is a colourless gas which smells like rotten egg (repulsive smell of a rotten egg).
2. It is an acidic gas which turns moist blue litmus to red.
3. It is a very poisonous gas.
4. It is denser than air (about 1.18 times)
5. It is moderately soluble in water.
6. It burns with a pale blue flame.
CHEMICAL PROPERTIES OF H2S
1. As an acid: H2S forms sulphides with bases and alkalis e.g.
NaOH(aq) + H2S(g) Na2S(aq) + 2H2O(l)
NaOH(aq) + H2S(g) NaHS(aq) + H2O(l)
Excess acid salt
2. As a reducing agent: H2S acts as a reducing agent and becomes oxidized to deposit sulphur e.g. 2FeCl3(aq) + H2S(g) 2FeCl2(aq) + 2HCl(aq) + S(s)
Reddish brown
Or brownish yellow
3. Reaction with oxygen: It combines with oxygen to form water and either sulphur or sulphur (IV) oxide depending on the amount of oxygen e.g.
2H2S (g) + O2 (g) 2H2O (l) + 2S(s)
Limited
Supply
2H2S (g) + 3O2 (g) 2H20(l) + 2SO2 (g)
Excess
supply
4. As a precipitating agent: H2S precipitates some coloured insoluble sulphide from their aqueous solution e.g.
ZnSO4 (aq) + H2S (g) ZnS(s) + H2SO4 (aq)
White
Pb(NO3)2(aq) + H2S(g) PbS(s) + 2HNO3(aq)
Black
TEST FOR H2S
1. SMELL: H2S has a repulsive smell like that of a rotten egg.
2. WITH LEAD (II) TRIOXONITRATE (v), Pb(NO3)2:
If a piece of filter paper moistened with Pb(NO3)2 solution is dropped into the gas, the lead (II) trioxonitrate (V) paper turns black due to the formation of black lead (II) Sulphide, PbS.
Pb(NO3)2 (aq) + H2S(g) PbS(s) + 2HNO3 (aq)
Black
3. WITH LEAD (II) ETHANOATE, Pb(CH3COO)2, PAPER
if lead (II) ethanoate paper is dropped into the gas, it turns black due to the formation of black lead (II) Sulphide, PbS.
Pb(CH3COO)2(aq) + H2S(g) PbS(s) + 2CH3COOH(aq)
Black
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List the physical properties of H2S.
ii. Use chemical equation to explain the acidic property of H2S.
iii. Use chemical equation to explain the reducing property of H2S with FeCl3.
ASSIGNMENT:
i. Give the physical test for H2S.
ii. Give two chemical tests for H2S.
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the uses of H2S.
b. Use chemical equations to explain the industrial preparation of H2SO4 by the contact process.
CONTENT: USES OF H2S
H2S is used in the analysis of ores and metals. Groups of metals can be separated from one another because their sulphides have different solubilities in acids and alkalis. The presence of a certain metal is often indicated by the colour of its sulphide.
TETAOXOSULPHATE (vi) ACID, H2SO4
H2SO4 is very commonly used in the laboratory and in the manufacturing sector.
INDUSTRIAL MANUFACTURE OF H2SO4
H2SO4 is prepared in the industry by the CONTACT PROCESS.
This involves the catalytic combination of sulphur (IV) oxide, SO2 and oxygenO2 (at S.P and 4500C – 5000C) to form Sulphur (IV) oxide, SO3; the catalyst is Vanadium (V) oxide, V2O5.
2SO2 (g) + O2 (g) 2SO3 (g) + HEAT
[SO2 is obtained by burning sulphur in dry air; S(s) + O2 (g) SO2 (g)]
The SO3 is cooled and is dissolved in conc. H2SO4 to form OLEUM.
SO3 (g) + H2SO4 (aq) H2S2O7 (aq)
Oleum
The oleum is then carefully diluted with calculated amounts of water to produce 98% H2SO4 used in the laboratory and other desired concentrations.
H2S2O7 (aq) + H2O (l) 2H2SO4 (aq)
Scheme of the contact process
S + O2 SO2 SO3 H2S2O7 2H2SO4
Oleum
O2 conc. H2SO4 H20
(Excess air)
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List the uses of H2s.
ii. With the aid of balanced chemical equations, explain the industrial manufacture of H2SO4.
ASSIGNMENT:
1. With the aid of a balanced chemical equation, explain how H2SO4 is obtained from oleum.
2. Use chemical equations only to show the chemical test for H2S.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the physical properties of H2SO4.
b. Explain the chemical properties of H2SO4 with the aid of chemical equations.
CONTENT: PROPERTIES OF H2SO4
PHYSICAL PROPERTIES:
1. Conc. H2SO4 acid is often called the OIL OF VITROIL and is a colourless, viscous liquid with a density of 1.84gcm-3.
2. Conc. H2SO4 acid is corrosive and causes severe burns if it comes into contact with the skin.
3. Conc. H2SO4 acid has a great affinity for water and gives out a large amount of heat as it dissolves in water.
4. Conc. H2SO4 is hygroscopic as it absorbs moisture (water vapour) from the surroundings and becomes more dilute in the process.
CHEMICAL PROPERTIES OF H2SO4
1. As an acid: It is a very strong dibasic acid and hence shows all the properties of acid e.g.
H2SO4 (aq) + 2KOH (aq) K2SO4 (aq) + 2H2O (l)
2. As a dehydrating agent: H2SO4 removes hydrogen oxygen in form of water when it is concentrated e.g.
Conc. H2SO4
C2H5OH C2H4
-H20
3. Displacement reaction: conc. H2SO4 displaces other acids from their salts e.g.
H2SO4 (aq) + 2NaCl (s) Na2SO4 (aq) + 2HCl (g)
H2SO4 (aq) + 2KNO3 (s) K2SO4 (aq) + 2HNO3 (g)
4. As an oxidizing agent: e.g.
Zn(s) + 2H2SO4 (aq) Zn2+SO42- (aq) + 2H20 (l) + SO2 (g)
EVALUATION: The teacher evaluates the lesson with the following questions:
a. List the physical properties of H2SO4.
b. Explain the chemical properties of H2SO4 with the aid of chemical equations.
ASSIGNMENT:
1. Explain hygroscopy as it relates to conc. H2SO4.
2. Use balanced chemical equations to illustrate the acidic property of H2SO4
PERIOD: 4
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the uses of H2SO4.
b. Explain the nature of tetraoxosulphate (VI) and give examples of these compounds.
c. Give the test for SO42-.
CONTENT: USES OF H2SO4
1) As an electrolyte in car battery (i.e. lead accumulator).
2) It is used in the production of fertilizers such as (NH4)2SO4 and CaH2(PO4)2.
3) It is used in making explosives.
4) It is used as a dehydrating agent.
5) It is used as a drying agent for many gases (except H2S ad NH3). It is also used in dessicators as a drying agent.
6) It is used in the manufacture of fabrics (artificial fabrics and natural fabrics), plastics and cellulose film.
7) It is used in the manufacture of many important chemical compounds e.g. HCl, HNO3 and sulphates of metals.
TETRAOXOSULPHATES (VI)
The tetraoxosulphates (VI) are the normal salts formed when all the replaceable hydrogen ions in H2SO4 are replaced by metallic or ammonium ions. Most tetraoxosulphate (VI) salts are crystalline and dissolve readily in water e.g. Na2SO4, K2SO4, (NH4)2SO4 are soluble salts. The important exceptions are CaSO4, PbSO4, Hg2SO4 which are anhydrous salts and insoluble in water.
TEST FOR SO42-
Acidify the aqueous solution with dilute HCl and then add BaCl2. A white precipitate is formed which is insoluble in excess dilute HCl if it is SO42-. But if it is SO32-, then the white precipitate formed will be soluble in excess dilute HCl.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. List four uses of H2SO4.
2. Give three examples each of soluble and insoluble tetraoxosulphate (VI) salts.
3. Give the chemical tests for SO42- and SO32-.
ASSIGNMENT:
1. Distinguish between the chemical tests for SO42- and SO32-.
2. Give the difference between drying agent and dehydrating agent.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List the physical properties of H2S.
b. Explain the chemical properties of H2S.
c. Give the test for H2S.
CONTENT: PHYSICAL PROPERTIES OF HYDROGEN SULPHIDE (H2S)
1. H2S is a colourless gas which smells like rotten egg (repulsive smell of a rotten egg).
2. It is an acidic gas which turns moist blue litmus to red.
3. It is a very poisonous gas.
4. It is denser than air (about 1.18 times)
5. It is moderately soluble in water.
6. It burns with a pale blue flame.
CHEMICAL PROPERTIES OF H2S
1. As an acid: H2S forms sulphides with bases and alkalis e.g.
NaOH(aq) + H2S(g) Na2S(aq) + 2H2O(l)
NaOH(aq) + H2S(g) NaHS(aq) + H2O(l)
Excess acid salt
2. As a reducing agent: H2S acts as a reducing agent and becomes oxidized to deposit sulphur e.g. 2FeCl3(aq) + H2S(g) 2FeCl2(aq) + 2HCl(aq) + S(s)
Reddish brown
Or brownish yellow
3. Reaction with oxygen: It combines with oxygen to form water and either sulphur or sulphur (IV) oxide depending on the amount of oxygen e.g.
2H2S (g) + O2 (g) 2H2O (l) + 2S(s)
Limited
Supply
2H2S (g) + 3O2 (g) 2H20(l) + 2SO2 (g)
Excess
supply
4. As a precipitating agent: H2S precipitates some coloured insoluble sulphide from their aqueous solution e.g.
ZnSO4 (aq) + H2S (g) ZnS(s) + H2SO4 (aq)
White
Pb(NO3)2(aq) + H2S(g) PbS(s) + 2HNO3(aq)
Black
TEST FOR H2S
1. SMELL: H2S has a repulsive smell like that of a rotten egg.
2. WITH LEAD (II) TRIOXONITRATE (v), Pb(NO3)2:
If a piece of filter paper moistened with Pb(NO3)2 solution is dropped into the gas, the lead (II) trioxonitrate (V) paper turns black due to the formation of black lead (II) Sulphide, PbS.
Pb(NO3)2 (aq) + H2S(g) PbS(s) + 2HNO3 (aq)
Black
3. WITH LEAD (II) ETHANOATE, Pb(CH3COO)2, PAPER
if lead (II) ethanoate paper is dropped into the gas, it turns black due to the formation of black lead (II) Sulphide, PbS.
Pb(CH3COO)2(aq) + H2S(g) PbS(s) + 2CH3COOH(aq)
Black
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List the physical properties of H2S.
ii. Use chemical equation to explain the acidic property of H2S.
iii. Use chemical equation to explain the reducing property of H2S with FeCl3.
ASSIGNMENT:
i. Give the physical test for H2S.
ii. Give two chemical tests for H2S.
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the uses of H2S.
b. Use chemical equations to explain the industrial preparation of H2SO4 by the contact process.
CONTENT: USES OF H2S
H2S is used in the analysis of ores and metals. Groups of metals can be separated from one another because their sulphides have different solubilities in acids and alkalis. The presence of a certain metal is often indicated by the colour of its sulphide.
TETAOXOSULPHATE (vi) ACID, H2SO4
H2SO4 is very commonly used in the laboratory and in the manufacturing sector.
INDUSTRIAL MANUFACTURE OF H2SO4
H2SO4 is prepared in the industry by the CONTACT PROCESS.
This involves the catalytic combination of sulphur (IV) oxide, SO2 and oxygenO2 (at S.P and 4500C – 5000C) to form Sulphur (IV) oxide, SO3; the catalyst is Vanadium (V) oxide, V2O5.
2SO2 (g) + O2 (g) 2SO3 (g) + HEAT
[SO2 is obtained by burning sulphur in dry air; S(s) + O2 (g) SO2 (g)]
The SO3 is cooled and is dissolved in conc. H2SO4 to form OLEUM.
SO3 (g) + H2SO4 (aq) H2S2O7 (aq)
Oleum
The oleum is then carefully diluted with calculated amounts of water to produce 98% H2SO4 used in the laboratory and other desired concentrations.
H2S2O7 (aq) + H2O (l) 2H2SO4 (aq)
Scheme of the contact process
S + O2 SO2 SO3 H2S2O7 2H2SO4
Oleum
O2 conc. H2SO4 H20
(Excess air)
EVALUATION: The teacher evaluates the lesson with the following questions:
i. List the uses of H2s.
ii. With the aid of balanced chemical equations, explain the industrial manufacture of H2SO4.
ASSIGNMENT:
1. With the aid of a balanced chemical equation, explain how H2SO4 is obtained from oleum.
2. Use chemical equations only to show the chemical test for H2S.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the physical properties of H2SO4.
b. Explain the chemical properties of H2SO4 with the aid of chemical equations.
CONTENT: PROPERTIES OF H2SO4
PHYSICAL PROPERTIES:
1. Conc. H2SO4 acid is often called the OIL OF VITROIL and is a colourless, viscous liquid with a density of 1.84gcm-3.
2. Conc. H2SO4 acid is corrosive and causes severe burns if it comes into contact with the skin.
3. Conc. H2SO4 acid has a great affinity for water and gives out a large amount of heat as it dissolves in water.
4. Conc. H2SO4 is hygroscopic as it absorbs moisture (water vapour) from the surroundings and becomes more dilute in the process.
CHEMICAL PROPERTIES OF H2SO4
1. As an acid: It is a very strong dibasic acid and hence shows all the properties of acid e.g.
H2SO4 (aq) + 2KOH (aq) K2SO4 (aq) + 2H2O (l)
2. As a dehydrating agent: H2SO4 removes hydrogen oxygen in form of water when it is concentrated e.g.
Conc. H2SO4
C2H5OH C2H4
-H20
3. Displacement reaction: conc. H2SO4 displaces other acids from their salts e.g.
H2SO4 (aq) + 2NaCl (s) Na2SO4 (aq) + 2HCl (g)
H2SO4 (aq) + 2KNO3 (s) K2SO4 (aq) + 2HNO3 (g)
4. As an oxidizing agent: e.g.
Zn(s) + 2H2SO4 (aq) Zn2+SO42- (aq) + 2H20 (l) + SO2 (g)
EVALUATION: The teacher evaluates the lesson with the following questions:
a. List the physical properties of H2SO4.
b. Explain the chemical properties of H2SO4 with the aid of chemical equations.
ASSIGNMENT:
1. Explain hygroscopy as it relates to conc. H2SO4.
2. Use balanced chemical equations to illustrate the acidic property of H2SO4
PERIOD: 4
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List and explain the uses of H2SO4.
b. Explain the nature of tetraoxosulphate (VI) and give examples of these compounds.
c. Give the test for SO42-.
CONTENT: USES OF H2SO4
1) As an electrolyte in car battery (i.e. lead accumulator).
2) It is used in the production of fertilizers such as (NH4)2SO4 and CaH2(PO4)2.
3) It is used in making explosives.
4) It is used as a dehydrating agent.
5) It is used as a drying agent for many gases (except H2S ad NH3). It is also used in dessicators as a drying agent.
6) It is used in the manufacture of fabrics (artificial fabrics and natural fabrics), plastics and cellulose film.
7) It is used in the manufacture of many important chemical compounds e.g. HCl, HNO3 and sulphates of metals.
TETRAOXOSULPHATES (VI)
The tetraoxosulphates (VI) are the normal salts formed when all the replaceable hydrogen ions in H2SO4 are replaced by metallic or ammonium ions. Most tetraoxosulphate (VI) salts are crystalline and dissolve readily in water e.g. Na2SO4, K2SO4, (NH4)2SO4 are soluble salts. The important exceptions are CaSO4, PbSO4, Hg2SO4 which are anhydrous salts and insoluble in water.
TEST FOR SO42-
Acidify the aqueous solution with dilute HCl and then add BaCl2. A white precipitate is formed which is insoluble in excess dilute HCl if it is SO42-. But if it is SO32-, then the white precipitate formed will be soluble in excess dilute HCl.
EVALUATION: The teacher evaluates the lesson with the following questions:
1. List four uses of H2SO4.
2. Give three examples each of soluble and insoluble tetraoxosulphate (VI) salts.
3. Give the chemical tests for SO42- and SO32-.
ASSIGNMENT:
1. Distinguish between the chemical tests for SO42- and SO32-.
2. Give the difference between drying agent and dehydrating agent.
WEEK 9
TOPIC: ORGANIC CHEMISTRY
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Define and explain organic chemistry.
2. List the compound elements of organic chemistry and the reason why there are numerous organic compounds.
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: INTRODUCTION TO ORGANIC CHEMISTRY
Organic chemistry: is the chemistry of carbon compounds with the exception of the oxides of carbon (CO, CO2) the trioxocarbonates (IV) and the metallic carbides.
Carbon has a tetravalent nature of four valence electrons and this must be fulfilled in its organic compounds as four single covalent bonds always.
Organic compounds are made of
(a) the main element, carbon;
(b) hydrogen and oxygen which are usually present and;
(c) Elements such as nitrogen, the halogens, phosphorus, sulphur and some metals which are sometimes present.
The reason for numerous organic compounds is due to the following properties of carbon.
(i) Catenation is the exceptional ability of carbon atoms to catenate by combingwith one another to form straight chains, branched chains or ring compounds containing many carbon atoms.
(ii) Carbon combines easily with hydrogen, oxygen, nitrogen and the halogens.
(iii) Carbon atoms can form single, double or triple covalent bonds.
(iv) These can be shown with five carbon atoms thus:
H H H H H H H H H
H - C C C C C - H H - C C C C – H
H H H H H H H H
H C H
H
(PENTANE) (2-METHYL BUTANE)
CHARACTERISTICS OF ORGANIC COMPOUNDS
1. They are covalent and thus do not ionize in solution and are non-conductors of electricity.
2. They have low melting and boiling points because of relatively weak inter molecular forces.
3. Most organic compounds are non-polar and are thus insoluble in water e.g. petrol, kerosene, and paraffin oil do not dissolve in water. But those containing polar group (-OH) are soluble in water (e.g. ethanol). Those with very electronegative elements like chlorine are polar in nature.
Non-polar substances like organic compounds dissolve only in non-polar solvents like benzene or ether.
4. Thermal instability which is of commercial importance as in the cracking of petroleum.
5. Flammability : Most organic compounds burn exothermically in air to yield CO2 and water. Thus, most fuels such as wood, coal, oil, petrol and natural gas are organic and their combustion provides our main source of heat energy.
6. Reactivity: Organic reactions are slower than the ionic reactions; thus, organic reactions usually require heating, thorough mixing and catalyst to speed up the reactions.
EVALUATION: The teacher evaluates the lesson with the following questions:
i. Define organic chemistry.
ii. Explain the properties of carbon that makes it to form numerous organic compounds.
iii. List six characteristics of organic compounds.
ASSIGNMENT:
1. Define catenation.
2. Use electronic configuration to explain the tetravalent nature of carbon.
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Define and explain homologous series.
b. Explain the characteristics of homologous series.
CONTENT: HOMOLOGOUS SERIES
Organic compounds can be classified as hydrocarbons (alkanes, alkenes, alkynes) alkanols, alkanoic acids, alkanoates, carbohydrates, fats and oils, proteins, amides etc.
A HOMOLOGOUS SERIES is a family of organic compounds which conforms to the same general molecular formular and each successive member differs from the next by a molecular formular difference of –CH2 group.
Examples of homologous series are:
1. Alkane (CnH2n+2)
2. Alkene (CnH2n)
3. Alkyne (CnH2n-2)
4. Alkanol (CnH2n+1OH)
5. Alkanoic acid (CnH2n+1COOH)
6. Alkanoate or Ester (CnH2n+1COOCnH2n+1:RCOOR1)
7. Alkanol or Aldehyde (CnH2n+1CHO)
8. Alkanone or Ketone R
C=0
R1
CHARACTERISTICS OF HOMOLOGOUS SERIES
1. General Molecular Formular: All members in a series conform to the same general molecular formula e.g. CnH2n+2 for alkanes [(CH4-methane0; (C2H6-ethane), (C3H8-propane)], CnH2n for the alkenes [(C2H4-ethene); (C3H6-propene); (C4H8-butene)].
2. Difference of –CH2 and molecular mass difference of 14: Successive members differ by –CH2 and 14 in the relative molecular mass e.g. CH4 (16); C2H6 (30); C3H8(44).
3. Physical properties: The physical properties of the members of a series change gradually as the number of carbon atoms per molecule increases e.g. the boiling points (b.pts) of alkanes increase down the series ( first four members of alkanes are gases while those with 5 to 17 c-atoms per molecule are volatile liquids).
4. Chemical properties: the members of a series show similar chemical reaction. For example all alkanes burn in air, forming CO2 and H2O; and they undergo substitution reactions with other substances such as halogens.
2C2H6 (g) + 7O2 (g) 4CO2 (g) + 6H2O (g)
Ethane
C2H6 (g) + Cl2 (g) C2H5Cl (g) + HCl (g)
C3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (g)
Propane
5. General Methods of Preparation: All members of the same series conform to the same general method of preparation e.g. all alkanes ca be prepared by action of hot soda0lime [quick lime, CaO, slaked with conc. NaOH] on the appropriate sodium alkanoate.
CH3COONa + NaOH Na2CO3 + CH4
Methane
C2H5COONa + NaOH Na2CO3 + C2H6
Ethane
C7H15COONa + NaOH Na2CO3 + C7H16
Heptane
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Define homologous series.
2. List and explain five characteristics of homologous series.
ASSIGNMENT:
1. Why are alkanols soluble in water?
2. Using chemical equation to show the general method of preparation, show how ethane and propane belong to the same homologous series.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Describe hydrocarbons.
b. List the classes of hydrocarbons.
c. List the sources of hydrocarbons.
d. Explain cracking and the two types of cracking (thermal cracking and catalytic cracking).
PREVIOUS KNOWLEDGE: The students should have the previous knowledge of
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: HYDROCARBONS
Hydrocarbons are compounds of carbon and hydrogen only. They have the general formula of CxHy where x and y are whole numbers. They can be classified into two:
a. ALIPHATIC HYDROCARBONS
b. AROMATIC HYDROCARBONS; according to their structures.
A. ALIPHATIC HYDROCARBONS: they have straight or branched chain and the cyclic ones have no alternating double bond. There are three classes of this : Alkanes, Akenes ad Alkynes.
Alkanes: CnH2n+ 2
H H H H
H C C C C H n- butane (normal butane)
H H H H
H H H
H C C C H 2- methylpropane
H H
H C H
H
Alkenes: CnH2n
H H H H
C = C C C H but-1-ene
H H H
H H H H
H C C = C C H but-2-ene
H H
H H H
H C C = C H 2-methylpropene
H
H C H
H
Alkynes: CnH2n-2
H H
H C C C C H but-1-yne
H H
H H
H C C C C H but-2-yne
H H
B. AROMATIC HYDROCARBONS
These are hydrocarbons of benzene derivatives which have ring structures with alternating double bonds.
H H
C C
H C C H H C
H C C H C H
C H C
H C H
C
Benzene H
[RESONANCE
HYBRID
STRUCTURE]
OH CH3 CH3
CH3
Phenol toluene xylene
SOURCES OF HYDROCARBONS
Coal, natural gas and petroleum are the natural sources of hydrocarbons. These natural sources are called FOSSIL FUELS because they are
1. The remains of plants and animals that died millions of years ago and
2. Used mainly as fuels, that is burnt to release heat or other forms of energy.
Coal is a solid fuel, petroleum is a dark, viscous liquid, fuel and natural gas is a gaseous fuel.
CRACKING OF PETROLEUM
Cracking of petroleum is the breaking down of heavier fractions of crude oil to obtain more desirable lower fractions (e.g. petrol, kerosene) of crude oil.
There are two types of cracking:
1. Thermal cracking
2. Catalytic cracking
EVALUATION: The teacher evaluates the lesson with the following questions:
a. List the two classes of hydrocarbons.
b. Draw the resonance hybrid structures of benzene.
c. Define cracking.
ASSIGNMENT:
1. List the two types of cracking
2. Draw the structural formulas of cyclohexane and benzene.
PERIOD: 4
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to:
a. Explain each of the two types of cracking
b. Explain saturated compounds with examples
c. Explain unsaturated compounds with examples.
CONTENT: TYPES OF CRACKING
1. Thermal cracking: is the use of vey high temperature (about 10000C), where heavy fractions of petroleum are broken down to more desirable lower fractions.
2. Catalytic cracking: involves the use of a catalyst (finely divided silica alumina catalyst) at a reduced temperature of 4500C to 5500C under a slight pressure to break down heavy fractions of crude oil into more desirable lower fractions.Catalytic cracking is better than thermal cracking because it is more controllable, i.e. the conditions can be adjusted to get desirable products of certain chain lengths. Secondly, it yields more petrol which is of high quality.
SATURATED AND UNSATURATED COMPOUNDS
A SATURATED compound contains atoms joined only by single covalent bonds. The alkanes are said to be saturated hydrocarbons e.g.
H H H H H
H C C H H C C C H
H H H H H
Propane ethane
AN UNSATURATED compound contains carbon atoms joined by double or triple covalent bonds. For example: Alkenes for double bonds and alkynes for triple bonds.
H H
C = C H C C H
H H ethyne
Ethene
Compounds which contain double or triple bonds between a carbon atom and an tom of another element can also be regarded as unsaturated e.g.
H H H
H C C = O H C C N
ethanol H ethanonitrite
means single covalent bond
means double covalent bond
means triple covalent bond
EVALUATION: The students should be able to :
a. Distinguish between thermal cracking and catalytic cracking.
b. Give two advantages of catalytic cracking over thermal cracking.
c. Define saturated compound with its homologous series example.
d. Define unsaturated compound with two homologous series hydrocarbon examples.
ASSIGNMENT:
1. How many electrons are shared in a single covalent bond and in a double covalent bond?
2. How many electrons are shared in a triple covalent bond? Illustrate this with structural example using ethyne.
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
1. Define and explain organic chemistry.
2. List the compound elements of organic chemistry and the reason why there are numerous organic compounds.
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: INTRODUCTION TO ORGANIC CHEMISTRY
Organic chemistry: is the chemistry of carbon compounds with the exception of the oxides of carbon (CO, CO2) the trioxocarbonates (IV) and the metallic carbides.
Carbon has a tetravalent nature of four valence electrons and this must be fulfilled in its organic compounds as four single covalent bonds always.
Organic compounds are made of
(a) the main element, carbon;
(b) hydrogen and oxygen which are usually present and;
(c) Elements such as nitrogen, the halogens, phosphorus, sulphur and some metals which are sometimes present.
The reason for numerous organic compounds is due to the following properties of carbon.
(i) Catenation is the exceptional ability of carbon atoms to catenate by combingwith one another to form straight chains, branched chains or ring compounds containing many carbon atoms.
(ii) Carbon combines easily with hydrogen, oxygen, nitrogen and the halogens.
(iii) Carbon atoms can form single, double or triple covalent bonds.
(iv) These can be shown with five carbon atoms thus:
H H H H H H H H H
H - C C C C C - H H - C C C C – H
H H H H H H H H
H C H
H
(PENTANE) (2-METHYL BUTANE)
CHARACTERISTICS OF ORGANIC COMPOUNDS
1. They are covalent and thus do not ionize in solution and are non-conductors of electricity.
2. They have low melting and boiling points because of relatively weak inter molecular forces.
3. Most organic compounds are non-polar and are thus insoluble in water e.g. petrol, kerosene, and paraffin oil do not dissolve in water. But those containing polar group (-OH) are soluble in water (e.g. ethanol). Those with very electronegative elements like chlorine are polar in nature.
Non-polar substances like organic compounds dissolve only in non-polar solvents like benzene or ether.
4. Thermal instability which is of commercial importance as in the cracking of petroleum.
5. Flammability : Most organic compounds burn exothermically in air to yield CO2 and water. Thus, most fuels such as wood, coal, oil, petrol and natural gas are organic and their combustion provides our main source of heat energy.
6. Reactivity: Organic reactions are slower than the ionic reactions; thus, organic reactions usually require heating, thorough mixing and catalyst to speed up the reactions.
EVALUATION: The teacher evaluates the lesson with the following questions:
i. Define organic chemistry.
ii. Explain the properties of carbon that makes it to form numerous organic compounds.
iii. List six characteristics of organic compounds.
ASSIGNMENT:
1. Define catenation.
2. Use electronic configuration to explain the tetravalent nature of carbon.
PERIOD: 2
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Define and explain homologous series.
b. Explain the characteristics of homologous series.
CONTENT: HOMOLOGOUS SERIES
Organic compounds can be classified as hydrocarbons (alkanes, alkenes, alkynes) alkanols, alkanoic acids, alkanoates, carbohydrates, fats and oils, proteins, amides etc.
A HOMOLOGOUS SERIES is a family of organic compounds which conforms to the same general molecular formular and each successive member differs from the next by a molecular formular difference of –CH2 group.
Examples of homologous series are:
1. Alkane (CnH2n+2)
2. Alkene (CnH2n)
3. Alkyne (CnH2n-2)
4. Alkanol (CnH2n+1OH)
5. Alkanoic acid (CnH2n+1COOH)
6. Alkanoate or Ester (CnH2n+1COOCnH2n+1:RCOOR1)
7. Alkanol or Aldehyde (CnH2n+1CHO)
8. Alkanone or Ketone R
C=0
R1
CHARACTERISTICS OF HOMOLOGOUS SERIES
1. General Molecular Formular: All members in a series conform to the same general molecular formula e.g. CnH2n+2 for alkanes [(CH4-methane0; (C2H6-ethane), (C3H8-propane)], CnH2n for the alkenes [(C2H4-ethene); (C3H6-propene); (C4H8-butene)].
2. Difference of –CH2 and molecular mass difference of 14: Successive members differ by –CH2 and 14 in the relative molecular mass e.g. CH4 (16); C2H6 (30); C3H8(44).
3. Physical properties: The physical properties of the members of a series change gradually as the number of carbon atoms per molecule increases e.g. the boiling points (b.pts) of alkanes increase down the series ( first four members of alkanes are gases while those with 5 to 17 c-atoms per molecule are volatile liquids).
4. Chemical properties: the members of a series show similar chemical reaction. For example all alkanes burn in air, forming CO2 and H2O; and they undergo substitution reactions with other substances such as halogens.
2C2H6 (g) + 7O2 (g) 4CO2 (g) + 6H2O (g)
Ethane
C2H6 (g) + Cl2 (g) C2H5Cl (g) + HCl (g)
C3H8 (g) + 5O2 (g) 3CO2 (g) + 4H2O (g)
Propane
5. General Methods of Preparation: All members of the same series conform to the same general method of preparation e.g. all alkanes ca be prepared by action of hot soda0lime [quick lime, CaO, slaked with conc. NaOH] on the appropriate sodium alkanoate.
CH3COONa + NaOH Na2CO3 + CH4
Methane
C2H5COONa + NaOH Na2CO3 + C2H6
Ethane
C7H15COONa + NaOH Na2CO3 + C7H16
Heptane
EVALUATION: The teacher evaluates the lesson with the following questions:
1. Define homologous series.
2. List and explain five characteristics of homologous series.
ASSIGNMENT:
1. Why are alkanols soluble in water?
2. Using chemical equation to show the general method of preparation, show how ethane and propane belong to the same homologous series.
PERIOD: 3
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Describe hydrocarbons.
b. List the classes of hydrocarbons.
c. List the sources of hydrocarbons.
d. Explain cracking and the two types of cracking (thermal cracking and catalytic cracking).
PREVIOUS KNOWLEDGE: The students should have the previous knowledge of
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)
CONTENT: HYDROCARBONS
Hydrocarbons are compounds of carbon and hydrogen only. They have the general formula of CxHy where x and y are whole numbers. They can be classified into two:
a. ALIPHATIC HYDROCARBONS
b. AROMATIC HYDROCARBONS; according to their structures.
A. ALIPHATIC HYDROCARBONS: they have straight or branched chain and the cyclic ones have no alternating double bond. There are three classes of this : Alkanes, Akenes ad Alkynes.
Alkanes: CnH2n+ 2
H H H H
H C C C C H n- butane (normal butane)
H H H H
H H H
H C C C H 2- methylpropane
H H
H C H
H
Alkenes: CnH2n
H H H H
C = C C C H but-1-ene
H H H
H H H H
H C C = C C H but-2-ene
H H
H H H
H C C = C H 2-methylpropene
H
H C H
H
Alkynes: CnH2n-2
H H
H C C C C H but-1-yne
H H
H H
H C C C C H but-2-yne
H H
B. AROMATIC HYDROCARBONS
These are hydrocarbons of benzene derivatives which have ring structures with alternating double bonds.
H H
C C
H C C H H C
H C C H C H
C H C
H C H
C
Benzene H
[RESONANCE
HYBRID
STRUCTURE]
OH CH3 CH3
CH3
Phenol toluene xylene
SOURCES OF HYDROCARBONS
Coal, natural gas and petroleum are the natural sources of hydrocarbons. These natural sources are called FOSSIL FUELS because they are
1. The remains of plants and animals that died millions of years ago and
2. Used mainly as fuels, that is burnt to release heat or other forms of energy.
Coal is a solid fuel, petroleum is a dark, viscous liquid, fuel and natural gas is a gaseous fuel.
CRACKING OF PETROLEUM
Cracking of petroleum is the breaking down of heavier fractions of crude oil to obtain more desirable lower fractions (e.g. petrol, kerosene) of crude oil.
There are two types of cracking:
1. Thermal cracking
2. Catalytic cracking
EVALUATION: The teacher evaluates the lesson with the following questions:
a. List the two classes of hydrocarbons.
b. Draw the resonance hybrid structures of benzene.
c. Define cracking.
ASSIGNMENT:
1. List the two types of cracking
2. Draw the structural formulas of cyclohexane and benzene.
PERIOD: 4
BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to:
a. Explain each of the two types of cracking
b. Explain saturated compounds with examples
c. Explain unsaturated compounds with examples.
CONTENT: TYPES OF CRACKING
1. Thermal cracking: is the use of vey high temperature (about 10000C), where heavy fractions of petroleum are broken down to more desirable lower fractions.
2. Catalytic cracking: involves the use of a catalyst (finely divided silica alumina catalyst) at a reduced temperature of 4500C to 5500C under a slight pressure to break down heavy fractions of crude oil into more desirable lower fractions.Catalytic cracking is better than thermal cracking because it is more controllable, i.e. the conditions can be adjusted to get desirable products of certain chain lengths. Secondly, it yields more petrol which is of high quality.
SATURATED AND UNSATURATED COMPOUNDS
A SATURATED compound contains atoms joined only by single covalent bonds. The alkanes are said to be saturated hydrocarbons e.g.
H H H H H
H C C H H C C C H
H H H H H
Propane ethane
AN UNSATURATED compound contains carbon atoms joined by double or triple covalent bonds. For example: Alkenes for double bonds and alkynes for triple bonds.
H H
C = C H C C H
H H ethyne
Ethene
Compounds which contain double or triple bonds between a carbon atom and an tom of another element can also be regarded as unsaturated e.g.
H H H
H C C = O H C C N
ethanol H ethanonitrite
means single covalent bond
means double covalent bond
means triple covalent bond
EVALUATION: The students should be able to :
a. Distinguish between thermal cracking and catalytic cracking.
b. Give two advantages of catalytic cracking over thermal cracking.
c. Define saturated compound with its homologous series example.
d. Define unsaturated compound with two homologous series hydrocarbon examples.
ASSIGNMENT:
1. How many electrons are shared in a single covalent bond and in a double covalent bond?
2. How many electrons are shared in a triple covalent bond? Illustrate this with structural example using ethyne.