Question

Give Reason Why...
( Question in attachment)​

Answer 1

Answer:

(b) It is done on sulphide ores in order to remove sulphur as sulphur escapes in the form of gas.

(c) Aluminum has a great affinity towards oxygen and so cannot be reduced by carbon, carbon monoxide or hydrogen, whereas lead oxide can be easily reduced to metal lead by carbon.

(d) As aluminium has great affinity for oxygen, so aluminium oxide is a stable compound. It is not easily reduced by common reducing agents like carbon, carbon monoxide or hydrogen. Hence, electrolytic reduction is chosen as the method for reducing alumina.

Answer 2

Answer!!

→ Carbonates, by loss of carbon dioxide, gets converted into oxide. This takes place when it is strongly heated and in the absence of air. Whereas when oxygen is provided to metallic sulphide, it gets converted into metallic oxide and sulphur dioxide when heated in the presence of air. The oxygen is provided during roasting so it is carried out on sulphide ores and not carbonate ores.

2ZnS + 3O₂ → 2ZnO + 2SO₂

→ Oxides of highly active metals like potassium, sodium, aluminium, calcium and magnesium have great electron affinity towards oxygen and so cannot be reduced by common reducing agents like coke, carbon monoxide or even hydrogen but lead oxide can be easily reduced by carbon with a simple chemical reaction.

2PbO + C → 2Pb + CO₂

→ Yes, electrolytic reduction is done of fused alumina which provides aluminium which is called Hall-Heroult's process. It can be done in molten state only. Alumina melts at approximately 2050°C. At this temperature, aluminium vaporises, so it was not easy to collect aluminium. This difficulty was removed by Hall who found a suitable solvent in another ore of alumina, cryolite (Na₃AlF₆). When he applied the current to the molten mixture of alumina (20%), cryolite (60%) and calcium fluoride (20%), he saw some shining globules of aluminium appearing at the cathode. This discovery revolutionised the aluminium industry and aluminium which was once a costlier and rarer metal than gold became a cheap metal of common use in every home.