What happens when

(i) When Na metal is dropped in water, it reacts violently to form sodium hydroxide and hydrogen gas. The chemical equation involved in the reaction is:

$2 \mathrm{Na}_{(s)}+2 \mathrm{H}_{2} \mathrm{O}_{(\prime)} \longrightarrow 2 \mathrm{NaOH}_{(a q)}+\mathrm{H}_{2(g)}$

(ii) On being heated in air, sodium reacts vigorously with oxygen to form sodium peroxide. The chemical equation involved in the reaction is:

$2 \mathrm{Na}_{(s)}+\mathrm{O}_{2(s)} \longrightarrow \mathrm{Na}_{2} \mathrm{O}_{2(s)}$

(iii) When sodium peroxide is dissolved in water, it is readily hydrolysed to form sodium hydroxide and water. The chemical equation involved in the reaction is:

$\mathrm{Na}_{2} \mathrm{O}_{2(s)}+2 \mathrm{H}_{2} \mathrm{O}_{(\vartheta)} \longrightarrow 2 \mathrm{NaOH}_{(a q)}+\mathrm{H}_{2} \mathrm{O}_{2(a q)}$