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(a) What is the role of cryolite in the metallurgy of aluminium ? (b) How is leaching carried out in case of low grade copper ores? (c) Why is zinc not extracted from zinc oxide through reduction using CO? |
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Answer» Solution :(a) Cryolite is added to bauxite ore before electrolysis because of the following reasons : (i) It ACTS as a solvent. (ii) It lowers the melting point of alumina to about 1173 K. (iii) Addition of cryolite to alumina INCREASES the electrical conductivity. (b) Copper is leached out from low grade copper by using acid in the presence of air when copper GOES into the solution as `Cu^(2+)`IONS. `Cu(s) + 2H^(+)(aq) + 1/2O_2(g) to Cu^(2+) (aq) + H_2O(l)` The solution containing` Cu^(2+)` ions is TREATED with scrap iron or `H_2`. `Cu^(2+) (aq) H_2(g) to Cu(s) + 2H^(+) (aq)` (c) In Ellingham diagram, the `DeltaG_r` vs T plot represcntingCO, `CO_2` lies above `DeltaG^@` vs T plot of Zn, ZnO. Therefore, CO cannot act as reducing agent for the reduction of ZnO. |
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