Answer. When acids react with sulphites and bisulphate’s salt, and SO2 gas is formed. For example, when hydrochloric acid reacts with calcium sulphite it produces calcium chloride and sulphur dioxide gas.
CaSO3 (aq) + 2HCl (aq) CaCI2 (aq) + SO2 (g) + H2O(1)
Similarly, hydrochloric acid reacts with sodium bisulphate to produce sodium chloride and sulphur dioxide gas.
NaHSO3 (aq) + HCl (aq) NaCl(aq) + SO2(g) + H2O(1)