Question 4
- (i) Describe briefly the industrial preparation of ammonia.
(ii) Write a balanced equation for the reaction in 4(a)(1).
(iii) State one way of increasing the yield of ammonia in 4(a)(i).
(iv) State two uses of ammonia. - Decsribe briefly, one chemical test for each of the following gases in the laboratory:
(i) hydrogen;
(ii) carbon (IV) oxide;
(iii) oxygen. - (i) State the composition of water gas.
(ii) List two uses of water gas. - Describe briefly a simple experiment to determine the type of hardness in a sample of water.
Observation
This question was not popular among the candidates, and few of them responded to it.
In part (a), majority of the candidates that responded to the question were able to describe the industrial preparation of ammonia.
In part (b), majority of the candidates did not write the observations when the chemical tests for hydrogen; carbon (IV) and oxygen were described. They wrote the description as a statement of fact.
In part (c), majority of the candidates listed two uses of water gas, and stated the composition of water gas.
In part (d), majority of candidates could not describe a simple experiment to determine the type of hardness in a sample of water.
The expected answers include
- (i) (Dry) nitrogen; (dry) hydrogen
Mixing in volume proportion of 1:3 respectively.
pressure of 200 – 500 atm
Catalyst (finely divided) iron at temp. of 450oC - 5000C
(iii) Continuous removal of ammonia as it is formed / liquefying the ammonia / low temperature / high pressure
(iv) - manufacture of fertilizers
- as a precipitating agent
- manufacture of trioxonitrate (V) acid
- manufacture of sodium trioxocarbonate (IV), textiles, pesticides
- used in detergents / cleaning agent
- manufacture of plastics
- laundry works
- pharmaceuticals
- as a refrigerant
- softening temporarily hard water
- removal of insect stings - (i) H2 - A lighted wooden splint is brought to the tip of a test tube containing the gas. The gas gives a ‘pop’ sound.
(ii) CO2 - Bubble gas through lime water / Ca(OH)2 solution. The lime water turns milky
(iii) O2 - A glowing (wooden) splint is dipped into a test tube of the gas(Wooden) splint rekindles / relights
- (i) Water gas - carbon (II) oxide / CO
- hydrogen / H2
(ii) - industrial manufacture of hydrogen / methanol / butanol
- fuel - Boil a sample of water add soap and shake if it forms lather easily it is temporary hardness if it forms lather with difficulty /does not form lather easily then it is permanent hardness.