Question 4
-
- Name one allotrope of oxygen.
- Draw a diagram for the laboratory preparation of dry oxygen gas from potassium trioxochlorate (V).
[6 marks]
- Ammonia is manufactured in the industry by the Haber process.
- State the source of the raw materials.
- Name two impurities removed during the purification of the materials.
- In what state is the final product collected.
- Give a reason for the answer given in 4(b)(iii).
-
- Name one solid which reacts with dilute hydrochloric acid to produce sulphur (IV) oxide.
- Describe a test for sulphur (IV) oxide.
- State how sulphur (IV) oxide behaves in 4(c)(ii).
- In the production of tetraoxosulphate (VI) acid, name two sources of sulphur.
[7 marks]
- Name one solid which reacts with dilute hydrochloric acid to produce sulphur (IV) oxide.
- (i) State three major chemical industries in Nigeria.
[6 marks]
(ii) List the raw material(s) used in each of the industries stated in 4(d)(i).
[6 marks]
Observation
This question was popular among the candidates because majority of them responded to it. However, only few of the candidates understood the demands of the question.
In part (a), majority of the candidates named one allotrope of oxygen. However, they could not draw a diagram for the laboratory preparation of dry oxygen gas from potassium trioxochlorate (V).
In part (b), majority of the candidates could not state the source of the raw materials for the industrial preparation of ammonia by Haber process.
In part (c), few candidates named one solid which reacts with dilute hydrochloric acid to produce sulphur(IV) oxide.Also, in stating the major chemical industries in Nigeria, majority of the candidates stated the brand names.
The expected answers include:
(a) 
(b)
(i) Nitrogen from air
Hydrogen from natural gas / petroleum / water gas
(ii)
- Dust particles
- Carbon (IV) oxide
- Water vapour
- Sulphur compounds / Sulphur
- Phosphorus compounds
- Carbon (II) oxide
- Hydrocarbons
- Oxides of nitrogen
(iii) In the liquid form
(iv) Because it has a high boiling point / to separate ammonia from unreacted nitrogen and hydrogen
(c)(i)
- sodium trioxosulphate (IV)
- potassium trioxosulphate (IV)
(ii)
- pass the gas into acidified KMnO4 solutionturns colourless
- test with acidified K2Cr2O7 solutionchanges to green
(iii) It behaves as a reducing agent
(iv)
- frasch process
- purification of natural gas
- refining of crude oil
- sulphur containing materials / pyrites
(d)