Which of the following salt would give `SO_2` with hot and dil. `H_2 SO_4` and also decolourise `Br_2` water?

Options

A. `Na_(2)SO_(3)`
B. `NaHSO_(4)`
C. `Na_(2)SO_(4)`
D. `Na_(2)S`

Answer

A

Explanation

When `Na_(2)SO_(3)` reacts with hot and dil `H_(2)SO_(4)` , it gives `SO_(2)`(g) which decolourises bromine-water. The reaction proceed as follows:
(i) `Na_(2) SO_(3) +H_(2) SO_(4) rarr Na_(2) SO_(4) + SO_(2)+H_(2)O`
(ii) `Br_(2) +H_(2)O rarr 2HBr + [O]`
(iii) `SO_(2) + [O] rarr SO_(3)`
(decolourisation of bromine-water)