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Answer the following questions briefly. ...

Answer the following questions briefly.
(i) What is the actual reducing agent of haematite in blast furnace ?
(ii) Give the equations for the recovery of lead from galena by air reduction.
(iii) Why is sodium chloride added during electrolysis of fused anhydrous magnesium chloride.
(iv) Zinc, not copper, is used for the recovery of metallic silver from the complex `[Ag(CN)_(2)]`. Explain.
(v) Why is chalcocite roasted and not calcinated during recovery of copper ?

Text Solution

Verified by Experts

Zinc is a very powerful reducing agent and readily displaces silver present in the complex.
`Zn + 2 [Ag(CN)_(2)]^(-) to underset("Soluble")([Zn(CN)_(4)]^(2-))+underset((ppt.))(2Ag)`
No doubt copper is also more reducing than silver but is not so effective as zinc. Moreover, zinc is cheaper than copper.
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