Question

Which of the following are true for roasting process:

• A. It removes arsenic and sulphur volatile impurities
• B. It converts sulphides to oxides
• C. It is carried out to form slag
• D. It removes the water of hydration

Answer 1

Answer: (A), (B)

It converts sulphides to oxides

(a) It removes arsenic and sulphur volatile impurities by converting them to their respective volatile oxides.
$2MS+3O_2\to 2MO+2S{O}_2$

(b) During roasting, the sulphide is converted to an oxide, and sulphur is released as sulphur dioxide, for example
$C{u}_{2}S+O_2\to C{u}_{2}O+S{O}_2$

(c) Roasting is a process of converting an ore into its oxide by heating strongly in presence of excess air.

(d) Roasting is not associated with the removal of water of hydration.