$(i)$ When a metal $X$ is added to the salt solution of a metal $Y$,the following chemical reaction takes place: Metal $X +$ Salt solution of $Y \rightarrow$ Salt solution of $X +$ Metal $Y$.
$(ii)$ Mention the inference you draw regarding the reactivity of metal $X$ and $Y$ and also about the type of reaction. State the reason for your conclusions.

Which is the oxidising agent in the following reaction?
$CuO(s) + H_2(g) \longrightarrow Cu(s) + H_2O(l)$

Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

When potassium iodide solution is added to a solution of lead $(II)$ nitrate in a test tube,a precipitate is formed.
$(i)$ What is the colour of this precipitate?
$(ii)$ Name the compound precipitated.

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?

Write the balanced chemical equations for the following reactions:
$(a)$ Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
$(b)$ Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride,water,and liberates carbon dioxide.
$(c)$ Copper sulphate on treatment with potassium iodide precipitates cuprous iodide $(Cu_2I_2)$,liberates iodine gas,and also forms potassium sulphate.