1.

Describe the principle of extraction of each of the following : (a) `Sn` from `SnO_(2)` (b) `Zn` frin `ZnO` ( c) `Cr` from `Cr_(2) O_(3)`.

Answer» (i) `Sn` from `SnO_(2)` : `SnO_(2)` is crushed, concentrared, roasted, and washed. It is smelted with powdered anthracite in blast furnace to obtain tin.
`SnO_(2) + 2e^(Ө) rarr Sn + 2CO`
(ii) `Zn` from `ZnO` : Zinc oxide is mixed with powdered coke and heated to `1673 K` in a fire day retort when it is reduced to zinc metal.
`ZnO +C overset(1673 K)rarrZn + CO`
(iii) `Cr` from `Cr_(2) O_(3)` : `Cr` is obtained from `Cr_(2)O_(3)` byaluminothermy process. In this process, a mixture of aluminium powder and `Cr_(2)O_(3)` is ignited in a closed crucible by inserting a burning magnesium ribbon into the ignition mixture consisting of magnesium power and barium peroxide.
`2Al + Cr_(2)O_(3) rarr Al_(2)O_(3) + 2Cr`.


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