#chemistry questions and answers

#Secondary Level Chemistry Form 3 Question Paper

Chemistry Form 3

Answer all questions

1 (a) Name the elements present in the following compounds

i. Calcium carbonate (1 1/2 mks )

ii. Ammonium nitrate (1 1/2 mks)

iii. Iron sulphate (1 mk)

iv. Tri-iron tetra oxide (1 mk)

b. Lead and copper have a valence of 2. Write the formula of

i. Lead (ii) carbonate (1mk)

a. Burning iron metal in oxygen (1mk)

b. Aluminium with dilute sulphuric acid (1mk)

c. Phosphorus (v) chloride with water (1mk)

iii. Ethane (2mks)

4. (a) Explain why copper (ii) sulphate salt cannot be prepared by precipitation method (2mks)

b. Briefly explain why salt of copper and lead cannot be prepared by action of dilute acids on copper and lead metal respectively (2mks)

5 (a) Define the following terms

i. Electrolyte (1mk)

ii. Conductors (1mk)

iii. Anode (1mk)

iv. Cathode (1mk)

b. Give one property of substances that are used as electrode in electrochemical cells (1mk)

c. Explain why solid copper (ii) sulphate does not conduct electricity while it conducts in aqueous state (3mks)

6. State three uses of graphite (3mks)

7. The valencies of metal X, Y and Z are 1, 2 and 3 respectively. Write the formulae of their respective hydroxides and phosphates (6mks)

8. Explain the following observations

a. Alkaline earth metals are generally less reactive than alkali metals (2mks)

b. The order of reactivity increases down group one but decreases down group seven (4mks)

9 (a) Both graphite and diamond are allotropes of carbon. Graphite conducts electricity while diamond does not. Explain (4mks)

b. State two physical properties of and two uses of diamond (4mks)

10. Given lead (ii) oxide, nitric acid, sodium carbonate and water, explain briefly how you can prepare lead carbonate. Use equations where possible (5mks)

11. (a) when a white solid x is heated, a yellow residue, brown gas and oxygen are formed.

Name:

i. Solid x (1mk)

ii. The yellow residue (1mk)

iii. The brown gas (1mk)

b. Write an equation for the decomposition of solid x (2mks)

c. Name two carbonates that don't decompose on heating (2mks)

16. (a) What is the purpose of polishing alkaline earth metals before using them in experiments (2mks)

(b) State four physical properties of alkali metals (4mks)