CHEMISTRY
TIME: 2:30HOURS AUGUST 2023
INSTRUCTIONS:
1. This paper consists of sections A, B and C with a total of fourteen (14) questions.
2. Answer all questions section A and B and only one questions in section C
3. All writing must be in blue or black ink except drawing which must be in pencil.
4. Cellular phones and any unauthorized materials are not allowed in the assessment room.
5. Write your examination number at the top of every page of your answer sheet.
6. The following constant may be used
· Atomic masses H=1, C=12, N=14, 0=16, Na=23, S=32, Ca= 40, Cl=35.5, Cu=64, Zn=64
· Avogadros number = 6.022 x 1023
· GMV at s.t.p = 22.4 dm3
· 1 Faraday =96,500 coulombs
· Standard pressure= 760 mmHg
· Standard temperature= 273 K
· 1 litre = 1 dm3 = 1,000cm3
SECTION A ( MARKS)
Answer all questions in this section
1. For each of the items (i) – (x) choose the correct answer from among the given alternatives and write its letter of the correct answer.
(i) The solution with the PH of 5 is
A. A strong base B. A neutral C. A weak acid
D. A strong acid E. A weak base
(ii) Which of the following is not a component of the first aid kit?
A. Goggles B. A pair of scissors C. Dropper
D. Gloves E. Razor blade
(iii) A rapid chemical reaction that release energy in form of light and heat is called
A. Combustion B. Decomposition C. Displacement
D. Neutralization E. Precipitation.
(iv) The molarity of a solution containing 26.5 g of anhydrous sodium carbonate in 5 dm3 of the solution is………………………M
A. 0.05 B. 0.25 C. 1.25 D. 5.3 E. 0.025
(v) Why oxygen differ from other gas?
A. It neither burns nor support combustion
B. It supports combustion but does not burn
C. It burns but does not support combustion.
D. It burns and supports combustion
E. It explodes and support combustion.
(vi) The oxidation state of chlorine in sodium chlorate (NaClO3) is
A. -1 B. +2 C. +5 D. +3 E. -3
(vii) Elements loose or gain electrons to form
A. Isotopes B. Radicals C. Molecules D. Ions E. Allotropes
(viii) Insoluble salts like barium sulphate generally can be obtained in the laboratory by
A. Evaporation B. Crystallization C. Precipitation
D. Decomposition E. Displacement
(ix) Most laboratory apparatus are made up of glass because
A. Is transparent B. Is unreactive C. Is readily available
D. Has high melting point E. Store chemicals for quite long
(x) The empirical formula differ from the molecular formula in a way that
A. Molecular formula may have higher mass
B. Empirical formula may have higher mass.
C. Always the empirical formula has lower mass.
D. Always the molecular formula has higher mass.
E. Empirical formula shows the simple ratio by mass while molecular formula shows actual number of atoms.
2. Match the items in list A with the responses in list B by writing the letter of the correct response beside the item number in the answer sheet
|
LIST
A |
LIST
B |
|
i) Bonding in molecules of
Nitrogen ii) Chemical equation iii) Biogas iv) Biomass v) Natural gas vi) Water gas |
A. Presentation of reactant and
products B. Industrial gas which is a
mixture of hydrogen and carbon monoxide. C. Triple bond. D. Non-renewable gaseous fuel. E. Industrial gases fuel which is
a mixture of nitrogen gas, hydrogen gas and carbon monoxide. F. Gas fuel derived from
decomposition of biological waste. G. Renewable source of energy. H. Water gas and ammonia. I. Ammonia and Butane. |
SECTION B (70 MARKS)
Answer all questions in this section
3. a) Giving an example for each, give four uses of matter in daily life (2 marks)
b) Why are chemical symbols useful in chemistry? Give reason
4. a) Distinguish between temporary hardness and permanent hardness of water.
b) By use of equations, show how each of the type of hardness in (a) above can be eliminated.
5. a) Define the following terms
(i) Acid
(ii) Base
(iii) Salt
(b) State any four importance of neutralization in daily life.
6. (a) Briefly explain three(3) importance of chemical equation.
(b) Give a balanced chemical equation between the reaction of sodium carbonate and hydrochloric acid.
7. (a) Calculate the concentration in g/dm3 of vinegar (CH3COOH) if 25cm3 of 0.01M Sodium hydroxide reacts with 12.5cm3 of vinegar.
(b) By giving a reason, suggest the suitable indicator for the reaction in (a) above.
8. (a) Explain the molar volume of a gas.
(b) If 0.5g of hydrogen gas is exploded in air, what is the mass of water formed/
9. (a) Element X has 20 electrons and mass number of 40. Work out the number of each type of nucleons present.
(b) Calculate the empirical formula and molecular formula of the compound having a relative molecular mass of 76 containing 15.8%, of carbon and 84.2% of sulphur.
10. a) How many Chlorine molecules are in 20cm3 of Chlorine gas at s.t.p.
(b)Calculate number of ions present in 5 g of copper (ii) nitrate.
11. (a) (i)What is laboratory
(ii) Name two main compound used in preparation of oxygen gas in laboratory
(iii) Why hydrogen gas is collected by downward displacement method?
(b) Complete and balance the following chemical reaction
(i) NaOH(aq) + HCl
(ii) NH4Cl(aq) + NaOH
(iii) Ca(OH)2(aq) + H2SO4(aq)
(iv) Mg(s) + HNO3(aq)
12. (a) In which other areas do we find the warning signs out of laboratory (give four points).
(b) Explain how measuring of volume differ when using measuring cylinder and burette.
SECTION C (15 MARKS)
Answer all questions on this section
13. (a) State Faradays laws of electrolysis.
(b) Dilute silver nitrate solution was decomposed by the passage of electric current through it. What mass of silver and what volume of oxygen (measured at s.t.p ) would be liberated in electrolysis liberated in electrolysis by 96500 coulombs of electricity.
(c) State three industrial application of electrolysis
14. (a) A form three student wanted to explain the properties of the sub atomic particles of an atom. Show how he will have to clarify the properties in the class of 40 students.
(b) Explain the Daltons contribution to atomic structure.
0 Comments