Question

Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> AIPMT 2007

Answer 1

The standard free energies of formation ${\Delta }_f{G}^0$ of most of the sulphides are greater than those of $C{S}_2$ and $H_{2}S$. Hence, neither carbon nor hydrogen can reduce metal sulphides to metal. The standard free energies of formation of oxides are much lower than those of $S{O}_2$. Therefore, oxidation of metal sulphides to metal oxides is thermodynamically favourable. Hence sulphide ore is roasted to the oxide before reduction.