Question

How will you differentiate between compounds containing sulphate and sulphite just by preliminary test?

Answer 1

Sulphate	Sulphite
On adding dilute hydrochloric acid, no gas is evolved.	On adding dilute hydrochloric acid, sulphur dioxide (SO2) gas is evolved.
There is no effervescence.	Effervescence occurs and the gas has a pungent, choking smell.
Hence, the absence of gas indicates the possible presence of sulphate ion.	Hence, the evolution of SO2 indicates the presence of sulphite ion.