Alkali metals oxide are obtained by combustion of the metals.Although Na normally gives `Na_2O_2`,it will take up further oxygen at elevated pressure and temperature to form `NaO_2`.The per and superoxides of the heavier alkalies can also be prepared by passing stoichiometric amounts of oxygen into their solution in liquid ammonia.
The different alkali metal oxides can be distinguished by reaction with water.The superoxides reacts with `CO_2` and give oxygen gas.The stability of per and superoxides is based upon that larger cation can stablise larger anion, due to larger lattice energy.
Alkali metals dissolve in liquid ammonia.Dilute solutions are dark blue in colour but as the concentration increases above 3M, the colour changes to copper bronze and the solution acquires the metallic lusture due to the formation of metal ions clusters.The solutions of alkali metals in liquid ammonia are good conductors of electricity due to the presence of ammoniated cations and ammoniated electrons.However, the conductivity decreases as the concentrations increases, since ammoniated electrons and ammoniated cation associate.
Select the correct choice for alkali metal oxides.

Options

A. Metal oxides react with water forming only metal hydroxides
B. Metal peroxides react with hot water forming metal hydroxides and oxygen gas
C. Metal superoxides react with water forming metal hydroxides , hydrogen peroxide and `O_2` gas
D. All of these

Answer

D

Explanation

(A)`M_2O +H_2O to 2MOH`
(B)`M_2O_2 + H_2O to 2MOH+1//2O_2`
(C )`2MO_2 + 2H_2O to 2MOH+H_2O_2 +O_2`