When dilute hydrochloric acid reacts with sodium sulphite, sulphur dioxide gas is evolved.
The reaction when hydrochloric acid reacts with sodium sulphite, it forms sodium chloride and sulphur dioxide which gives the smell of burning sulphur.
Na2SO3 + 2HCl → 2NaCl + H2O + SO2
It is a colourless gas having the suffocating smell of burning sulphur. When the evolved sulphur dioxide gas is passed through a potassium dichromate solution, the colour of the solution changes from orange to green.