What happens when an aquous solution of `SO_(2)` is heated in a sealed tube at 425K ?

Explanation

`SO_(2)` combines water to form sulphurous acid.
`SO_(2)(g) + H_(2)(l) to H_(2)SO_(3)(aq)`
When heated in a sealed tube `H_(2)SO_(3)` undergoes disproportion reaction to yield `H_(2)SO_(4)` and yellow coloured sulphur which precipitates.