Question

Dilute sulphuric acid is added to sodium sulphite. The following observations are noticed:

P A gas with a suffocating smell is evolved which turns lime water milky.

Q A foul smelling gas is evolved which turns lead acetate solution black.

R A gas is evolved which decolourises pink KMnO.

Which of the following is true?

Options

• Only P

• Only Q

• Only R

• Both P and R

Answer 1

Both P and R

Explanation:

Dilute sulphuric acid reacts with sodium sulphite to produce sulphur dioxide (SO₂).

\[\ce{Na2SO3 + H2SO4 −> Na2SO4 + H2O + SO2}\]

SO₂ has a suffocating smell, turns lime water milky, and decolourises pink KMnO₄ solution. It does not turn lead acetate solution black.