Question

Which one is mismatched ?

• A. Poling - refining of copper
• B. Cupellation - refining of silver
• C. Smelting - An oxidation process
• D. Roasting - An oxidation process

Answer 1

The correct option is C Smelting - An oxidation process

Poling: The molten impure metal (Cu) containing oxides as impurities is stirred with green poles of wood which releases hydrocarbon gases. The hydrocarbon gases reduces oxide to metal. It is used in refining of copper.

Cupellation: Pb present in Ag is removed by this method. The impure metal is heated in a cupel or oval shaped crucible made of bone ash or cement and blast of air is passed over the molten mass. The impurities get oxidised and removed with the blast of air. It is used in refining of silver.

Smelting: The process of extraction of metal in its molten state by any reducing agent in presence of flux is called smelting. For example: oxides of less electropositive metals like Pb, Zn, Fe, Cu are reduced by any other reducing agents. Thus, smelting is a reduction process and not an oxidation process.

Roasting: The process in which the concentrated ore is heated in blast of air and ore gets converted into oxide and impurities like sulphur, arsenic are also oxidised to their oxides and is removed is called Roasting. It requires very high temperature and specialized furnace like Bessemer or reverberatory furnace. Thus, it is an ixidation process.