Question

An ore contains arsenic and antimony as impurities. How are they removed during the process of roasting?

• A. By conversion into $A{s}_2{O}_3$ and $S{b}_2{O}_3$
• B. By conversion into $A{s}_2{O}_5$ and $S{b}_2{O}_5$
• C. By conversion into both trioxides and pentoxide
• D. By conversion into sulphides

Answer 1

The correct option is A By conversion into $A{s}_2{O}_3$ and $S{b}_2{O}_3$

Roasting is the process of strongly heating the ore into oxide in an unlimited supply of air. This process is commonly used for sulfides ores.

Impurities of non-metal like sulfur, arsenic, phosphorus, etc are oxidized and removed as a volatile gas. These impurities on reaction with oxygen gas produce oxides of non-metal which are gases of volatile nature.

Arsenic and antimony as impurities are removed as:

$As\left(s\right)+O_2\left(g\right)\to A{s}_2{O}_3\left(g\right)$

$Sb\left(s\right)+O_2\left(g\right)\to S{b}_2{O}_3\left(g\right)$

Hence, option A is correct.