Assertion (A): In aqueous solution, `SO_(2)` reacts with `H_(2)S` liberating sulphur
Reason (R ): `SO_(2)` is an effective reducing agent.

Options

A. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`.
B. If both `(A)` and `(R )` are correct but `(R )` is not the correct explanation of `(A)`.
C. If `(A)` is correct but `(R )` is incorrect.
D. If `(A)` and `(R )` are incorrect.

Answer

B

Explanation

Both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation for (A). `SO_(2)` can act both as an oxidising agent and a reducing agent, but in this reaction, `SO_(2)` is an oxidising agent and `H_(2)S` is a reducing agent.
`SO_(2)+2H_(2)SrarrS+2H_(2)O`
`S^(2-)rarrS+2e^(-)` (Oxidation) ( Reducing agent)
`4e^(-)+SO_(2)rarrS` (reduction) (Oxidising agent)