On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite,a white precipitate is obtained.
$(a)$ Write a balanced chemical equation of the reaction involved.
$(b)$ What other name can be given to this precipitation reaction?
$(c)$ On adding dilute hydrochloric acid to the reaction mixture,the white precipitate disappears. Why?

(A) The balanced chemical equation is:
$Na_{2}SO_{3}(aq) + BaCl_{2}(aq) \rightarrow BaSO_{3}(s) + 2NaCl(aq)$
$(b)$ This reaction is also known as a double displacement reaction.
$(c)$ $BaSO_{3}$ is a salt of a weak acid,sulphurous acid $(H_{2}SO_{3})$. When dilute hydrochloric acid $(HCl)$ is added,it reacts with the insoluble barium sulphite to form soluble barium chloride,water,and sulphur dioxide gas. The reaction is:
$BaSO_{3}(s) + 2HCl(aq) \rightarrow BaCl_{2}(aq) + H_{2}O(l) + SO_{2}(g)$
Since $BaCl_{2}$ is soluble in water,the white precipitate disappears.