Chemistry
(i) Name a metal found abundantly in the earth's crust.
(ii) Difference between calcination and roasting?
(iii) Name the process used for the enrichment of sulphide ore.
(iv) Write the chemical formulae of one main ore each of iron and aluminium.
(v) Write the constituents of the electrolyte for the extraction of aluminium.
Metallurgy
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Answer
(i) Aluminium is found abundantly in the earth's crust.
(ii) Difference between calcination and roasting is as follows:
| Calcination | Roasting |
|---|---|
| It is the process of heating the concentrated ore in a limited supply or absence of air at a temperature not sufficient to melt the ore. | It is the process of heating the concentrated ore in the presence of excess air to a high temperature before it is reduced to a metal. |
| Generally carbonate ores are calcinated and hence carbon dioxide is given out | Generally sulphide ores are roasted and hence sulphur dioxide is given out. |
(iii) Froth floatation process
(iv) Chemical formula of ores are :
Haematite ⟶ Fe2O3 : Ore of iron
Bauxite ⟶ Al2O3.2H2O : Ore of aluminium
(v) Constituents of electrolyte are :
Fused Alumina (Al2O3) — 1 part by weight.
Cryolite (Na3AlF6) — 3 part by weight.
Fluorspar (CaF2) —1 part by weight.
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