Question

In which of the following reactions of $H_{2}S{O}_4$, sulphur retains its oxidation state?

• A. Reaction of dil. $H_{2}S{O}_4$ with sulphur.
• B. Reaction of conc. $H_{2}S{O}_4$ with sulphur.
• C. Reaction of conc. $H_{2}S{O}_4$ with glucose.
• D. Reaction of dilute $H_{2}S{O}_4$ with zinc.

Answer 1

Answer: (C), (D)

The correct options are
C Reaction of conc. $H_{2}S{O}_4$ with glucose.
D Reaction of dilute $H_{2}S{O}_4$ with zinc.

When dilute sulphuric acid reacts with Sulphur, the following reaction takes place:

$2H_{2}S{O}_4$ $+$ $S$ $⟶$ $3S{O}_2$ $+$ $2H_{2}O$

Sulphur changes its oxidisation state from +6 to +4 ($H_{2}S{O}_4)$ and 0 to +4 $\left(S\right)$. Hence it reduce reaction.

The similar reaction takes place with concentrated Sulphuric acid. Hence in both cases oxidation state of Sulphur changes.

When Conc. $H_{2}S{O}_4$ reacts with glucose, the following reaction takes place:

$6H_{2}S{O}_4$ $+$ $C_6{H}_{12}{O}_6$ $⟶$ $6C$ $+$ $6H_{2}S{O}_4$ $+$ $H_{2}O$

So oxidation state of sulphur remain same.

When diluted $H_{2}S{O}_4$ reacts with $Zn$ , the following reaction takes place:

$Zn\left(s\right)$ $+$ $H_{2}S{O}_4\left(aq\right)$ $⟶$ $ZnS{O}_4\left(aq\right)$ $+$ $H_2\left(g\right)$

So, in this case also, the oxidation state of sulphur reamin same.