Question

Indicate in each reaction which one is oxidised or reduced if any:

$2N{a}_{2}S+4HCl+S{O}_3\to 4NaCl+3S+2H_{2}O$
In the above reaction, which one of the following is oxidised?

• A. $N{a}_{2}S$
• B. $HCl$
• C. $NaCl$
• D. None of these

Answer 1

The correct option is A $N{a}_{2}S$

The chemical equation is $2N{a}_{2}S+4HCl+S{O}_3\to 4NaCl+3S+2H_{2}O$.
The oxidation number of S increases from -2 (in $N{a}_{2}S$) to 0 (in S).
Hence, $N{a}_{2}S$ is oxidized.
The oxidation number of S decreases from +6 (in $S{O}_3$) to 0 (in S).
Hence, $S{O}_3$ is reduced.