(a) (i) List the two gaseous fuels produced from coke.
(ii) Which of the two fuels listed in 5(a)(i) is a better fuel?
(iii) Give reasons for your answer in 5(a)(ii)
(iv) Write a balanced equation for the production of each of the fuels. [9 marks]
(b)(i) Differentiate between thermosets and thermoplastics.
(ii) Give one example of:
I. thermosets;
II. thermoplastics.
(iii) State three properties of plastics.
(c)(i) State the method of collecting gases which are denser than air.
(ii) Name two gases that could be used to perform the fountain experiment in the laboratory.
(iii) State the physical properties of the gases named in 5(c)(ii) which makes them suitable for the experiment. [4 marks]
(d) (i) State two compounds that could be used to test for water.
(ii) Give three disadvantages of hard water.
Explanation
This is a popular question among the candidates.
In part (a), majority of the candidates listed the two gaseous fuels produced from coke.
In part (b), majority of the candidates could not differentiate between thermosets and thermoplastics. They could not give one example thermosets and thermoplastics.
In part (c), majority of the candidates stated the method of collecting gases which are denser than air. Also, majority of them named two gases that could be used to perform the fountain experiment in the laboratory.
In part (d), majority of the candidates stated two compounds that could be used to test for water. They gave three disadvantages of hard water.
The expected answers include:
(a)(i) - producer gas
-water gas
(ii) Water gas
(iii) It is because producer gas contains about 67% / more non-combustible nitrogen
and 33% / less of combustible carbon (II) oxide while water gas consist of equal amounts of combustible carbon (II) oxide and hydrogen.
(iv) - 2C(s) + O\(_2\) + 4N\(_2\) → 2CO + 4N\(_2\)
- C(s) + H\(_2\)O(g) → CO(g) + H\(_2\)(g)
(b)(i) Thermoplastics can be softened by heat and remoulded while thermosets cannot be softened by heat and remoulded once they are formed or set.
(ii) Examples:
Thermosets:
Urea-methanal
Polyvinyl chloride (p.v.c.)
Bakelite
Thermoplastics:
Polyethene
Polypropene/ Polyamide
Nylon
Perspex
Polystyrene
Terylene
(iii)- good insulators
- can be recycled/softened and reshaped
- are non-biodegradable
- can be tailor – made to exact requirements
- resistance to corrosion
- water-proof
(c)(i) Upward displacement of air / downward delivery
(ii) - hydrogen chloride
- ammonia
- sulphur (IV) oxide
(iii) The gases are highly/very soluble in water.
(d)(i) - copper (II) tetraoxosulphate (VI)/CuSO\(_4\)
- cobalt (II) chloride/CoCl\(_2\)
(ii) - wastes soap/forms scum/costs a lot of money to soften/does not readily lather with soap
- causes furring/scales in kettles / boilers
- cannot be used in dyeing / tanning