For each of the items (i) - (x), choose the correct answer from the given alternatives and write its letter in the answer booklet provided.
A.Ice → gas, Solid → gas → ice
B.Liquid → ice → gas
C.Gas → ice → liquid, Liquid → gas → ice
D.Ice → gas → liquid
E.Ice → liquid → gas, Gas → liquid → ice
2.1 mark
Which one is the molecular formula of a hydrocarbon having 20% hydrogen and vapour density of 15?
A.CH₄
B.C₂H₆
C.C₃H₈
D.C₄H₁₀
E.C₅H₆
12.1 mark
What is the molar mass of H$_2$SO$_4$? (Atomic masses: H=1, S=32, O=16)
A.60 g/mol
B.78 g/mol
C.98 g/mol
D.118 g/mol
13.1 mark
Which of the following is an example of a chemical change?
A.Melting of ice
B.Boiling of water
C.Burning of wood
D.Dissolving salt in water
14.1 mark
What is the atomic number of Zinc (Zn)?
A.30
B.65
C.35.5
D.12
15.1 mark
Which gas is produced during the electrolysis of water?
A.Oxygen only
B.Hydrogen only
C.Hydrogen and Oxygen
D.Carbon dioxide
16.1 mark
A substance that speeds up a chemical reaction without being consumed is called a(n):
A.Inhibitor
B.Catalyst
C.Reactant
D.Product
Section B
3.6 marks
(a)
Briefly explain six economic activities that depend on water.
6 mk
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4.10 marks
Consider the element G with atomic number 17, electronic configuration 2:8:7 and another element H with atomic number 11, electronic configuration 2:8:1. A and B represent the atomic number and mass number of element G respectively. C and D represent the atomic number and mass number of element H respectively. Write the electronic configuration of element G and H.
(a)
(i) Justify the fact that hydrogen has got both properties of group I and group VII elements. Give two points.
4 mk
(ii)
Why hydrogen is placed in group I rather than group VII in the Periodic Table?
2 mk
(b)
Given the atomic number of element G is 17 and its electronic configuration is 2:8:7, and the atomic number of element H is 11 and its electronic configuration is 2:8:1. State the group and period of element G and H. Predict the type of bond formed between element G and H and write the chemical reaction of sodium metal with element G and H.
4 mk
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5.10 marks
(a)
A student is investigating the effect of stirring on the dissolution of solid solute in a fixed volume of water while altering the temperature of the water. Categorize each variable in this experiment.
6 mk
(b)
Identify six steps to follow when conducting a scientific investigation.
4 mk
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6.10 marks
(a)
A certain chemist proposed the use of hydrogen gas as a fuel in vehicles. Suggest three advantages and three disadvantages of using the gas as a fuel.
6 mk
(b)
Why chemists prefer zinc granules and dilute hydrochloric acid to pure zinc and concentrated hydrochloric acid in the laboratory preparation of hydrogen gas?
4 mk
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7.8 marks
Identify six steps to follow in lighting the Bunsen burner so as to produce a non-luminous flame.
Give four uses of non-luminous flame and for each use indicate the property of the flame that is concerned.
(a)
Identify six steps to follow in lighting the Bunsen burner so as to produce a non-luminous flame.
6 mk
(b)
Give four uses of non-luminous flame and for each use indicate the property of the flame that is concerned.
2 mk
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8.12 marks
A soft water from a river was found to contain the following impurities: dissolved oxygen, suspended solids, dissolved carbon dioxide, and dissolved calcium carbonate. What experiment can be done to determine the amount of dissolved oxygen in the water? Write the equation for the reaction that occurs when sodium carbonate is added to the available water so as to perform the experiment. Under no circumstances, all the dissolved salts can be added to the available water to perform the experiment.
Explain each of the following cases with support of ionic equation:
Explain three advantages of hardness of water in daily life.
(a)
A soft water from a river was found to contain the following impurities: dissolved oxygen, suspended solids, dissolved carbon dioxide, and dissolved calcium carbonate. What experiment can be done to determine the amount of dissolved oxygen in the water? Write the equation for the reaction that occurs when sodium carbonate is added to the available water so as to perform the experiment. Under no circumstances, all the dissolved salts can be added to the available water to perform the experiment.
4 mk
(b)
Explain each of the following cases with support of ionic equation:
The temporary hardness of water can be removed by addition of washing soda.
5 mk
(c)
Explain three advantages of hardness of water in daily life.
3 mk
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Section C
9.10 marks
Briefly explain Le Chateliers principle.
A process Z is compromise of a reaction involving gaseous reactants X and Y as shown in the following equation:
X(g) + Y(g) ⇌ Z(g) ΔH=+ve kJmol⁻¹
By applying Le Chateliers principle, explain four technical ways through which the company can apply to increase the high yield of product Z.
(a)
Briefly explain Le Chateliers principle.
2 mk
(b)
A process Z is compromise of a reaction involving gaseous reactants X and Y as shown in the following equation:
X(g) + Y(g) ⇌ Z(g) ΔH=+ve kJmol⁻¹
By applying Le Chateliers principle, explain four technical ways through which the company can apply to increase the high yield of product Z.
8 mk
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10.10 marks
Describe the chemical properties of ethanol with respect to each of the following treatments:
(a)
Combustion in air
2 mk
(b)
Reaction with sodium metal
2 mk
(c)
Reaction with concentrated sulphuric acid at 170°C.
2 mk
(d)
Oxidation by acidified potassium dichromate
2 mk
(e)
Reaction with ethanoic acid.
2 mk
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11.10 marks
A certain company offers sulphur. How can you back-guide the investor to extract the sulphur based on the following points? Support you are answer with a well-drawn diagram.
The equipment involved during extraction.
The process during extraction.
Conversion of rhombic sulphur to monoclinic sulphur.
Two commercial uses of sulphur.
(a)
The equipment involved during extraction.
3 mk
(b)
The process involved during extraction.
3 mk
(c)
Conversion of rhombic sulphur to monoclinic sulphur.
2 mk