A metallic oxide reacts with water to form its hydroxide, hydrogen peroxide and also liberates oxygen. The metallic oxide could be

Potassium Superoxide react with water to produce potassium hydroxide, hydrogen peroxide and oxygen. This reaction
takes place at a temperature near \( 0^{\circ} \mathrm{C} \). Whereas, other metal oxide reacts with water but does not produce peroxide.
\( 2 \mathrm{KO}_{2}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{KOH}+\mathrm{H}_{2} \mathrm{O}_{2}+\mathrm{O}_{2} \)
Reaction of other metal
\( \mathrm{Na}_{2} \mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 4 \mathrm{NaOH}(a q)+\mathrm{O}_{2}(g) \) \( \mathrm{CaO}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_{2} \) \( \mathrm{Li}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{LiOH} \)