Question

When sodium sulphite reacts with the dilute hydrochloric acid, salt X, water and gas Y is formed. Gas X decolourised pink potassium permanganate solution. Gas X is:

• A. H₂
• B. SO₂
• C. CO₂
• D. Cl₂

Answer 1

The correct option is B

SO₂

When sodium sulphite reacts with the dilute hydrochloric acid, sodium chloride, water and sulphur dioxide gas is formed.

$N{a}_{2}S{O}_3+2HCl\to 2NaCl+H_{2}O+S{O}_2$

Sulphur dioxide gas is colourless with a smell of burning sulphur i.e., suffocating odour. It turns moist blue litmus red and finally bleaches it. It decolourises pink potassium permanganate solution.

$\underset{Pink}{2KMn{O}_4}+2H_{2}O+5S{O}_2\to \underset{colourless}{K_{2}S{O}_4}+2MnS{O}_4+2H_{2}S{O}_4$