Question

Copper is extracted from copper pyrites by

• A. Thermal decomposition
• B. Reduction by coke
• C. Electrometallurgy
• D. Auto reduction

Answer 1

Answer: (D)

The formula of copper pyrites is $CuFe{S}_2.$ In auto reduction, the sulphide ores of the metals which are less electropositive like $Hg,Pb$ and $Cu$ are heated in the air so as to convert a part of it to its oxides. These oxides then react with the remaining sulphide ore in the absence of air, to give the metal and sulphur dioxide. The corresponding reaction is:

$C{u}_{2}O+(1/2)C{u}_{2}S\to 3Cu+(1/2)S{O}_2$