(a) (i) List two gaseous pollutants that can be generated by burning coal.
(ii) Explain briefly why coal burns more easily when it is broken into pieces than when it is in lumps.
(iii What gas is responsible for most of the explosions in coal mines?
(iv) Name the non-volatile residue left behind after the destructive distillation of coal.
(b) State one oxide in each case which:
(i) is used in bleaching;
(ii) oxidizes hot concentrated HCl to chlorine;
(iii) dissolves in water to give a solution with pH greater than 7;
(iv) reacts with NaOH and also with HCl;
(v) is a reddish-brown gas.
(c) (i) Write a balanced chemical equation for the reaction between chlorine gas and iron(II) chloride solution.
(ii) State the type of reaction in (c)(i).
(iii) Give a reason for your answer in (c)(ii).
(d) Consider the following set-up:
(i) Identify A and B.
(ii) Write a balanced chemical equation for the reaction.
(iii) Name the gas produced.
(iv) Why was the flask tilted downwards?
(v) What is the:
(I) function of B in the experiment;
(II) method of collection of the gas?
(e) Give one product obtained from refining petroleum that is solid.
Explanation
(a) (i) - sulphur (IV) oxide /SO\(_2\)
- nitrogen (IV) oxide / NO\(_2\)
- nitrogen (II) oxide / NO
- carbon (II) oxide / (CO)
- methane / CH\(_4\)
(ii) Large lumps have smaller surface area to volume ratio than the broken pieces which has a greater surface area / increased exposed surface area. This makes the broken pieces to collide more frequently.
OR
The greater the rate of frequency of successful collisions, the greater the rate of reaction hence for the pieces of coal more reactant particles are exposed at the surface thereby increasing the frequency of successful collisions between reactant particles.
(iii) methane gas / CH\(_4\)
(iv) coke / carbon
(b) (i) - chlorine dioxide / (ClO\(_2\))
- sulphur (IV) oxide SO\(_2\)
- hydrogen peroxide / H\(_2\)O\(_2\)
- sodium peroxide Na\(_2\)O\(_2\)
(ii) - Manganese (IV) oxide / MnO\(_2\)
- Lead (IV) oxide / PbO2\(_2\)
(iii) - CaO
- MgO
- Na\(_2\)O
- K\(_2\)O
(iv) Aluminium oxide (Al\(_2\)O\(_3\)), ZnO, PbO, SnO\(_2\), SnO, PbO\(_2\)
(v) - nitrogen (IV) oxide / NO2\(_2\)
(c) (i)
(ii) Redox reaction
(iii) Because Iron (II) ions is oxidized to iron (III) ions / chlorine is reduced to chloride ions / chlorine gas oxidizes iron (II) ions to iron (III) ions and in the process chlorine is reduced to chloride ions / oxidation number of iron increases from +2 to +3 while that of chlorine decreases from 0 to -1.
(d) (i)
A - delivery tube
B - Calcium oxide / CaO / quicklime
(ii)
(iii) Ammonia
(iv) To prevent the (round bottom) flask from cracking / to prevent the water / steam formed from condensing into the hot glass flask.
(v) (I) Drying agent / To dry the gas
(II) Upward delivery / downward displacement of air
(e) - Paraffin wax
- Asphalt / bitumen