Question

On combustion in excess of air sodium mainly forms:

• A. $N{a}_{2}O$
• B. $N{a}_2{O}_2$
• C. $Na{O}_3$
• D. None

Answer 1

The correct option is B $N{a}_2{O}_2$

All alkali metals forms various oxide while heating in presence of air. They form monoxide, peroxide and also superoxides.

Sodium on limited amount of oxygen form sodium monoxide. In excess $O_2$, the formed monoxide will reacted with excess oxygen to form $N{a}_2{O}_2$.
$Na+\frac{1}{2}{O}_2\to N{a}_{2}O$; $N{a}_{2}O+\frac{1}{2}{O}_2\to N{a}_2{O}_2$
$N{a}_2{O}_2$ is the main product of the reaction. $N{a}_2{O}_2$ is pale yellow in colour and is a poweful oxidant and used in industries for bleaching paper and fabrics.