A metal on combustion in excess air forms $\mathrm{X}$, $\mathrm{X}$ upon hydrolysis with water yields $\mathrm{H}_{2} \mathrm{O}_{2}$ and $\mathrm{O}_{2}$ along with another product. The metal is:

JEE Main · 2019 · 12 Jan 2019 · Shift 1 · s-Block Elements

A metal on combustion in excess air forms

X

X

upon hydrolysis with water yields

H_{2} O_{2}

and

O_{2}

along with another product. The metal is:

Answer: (B)

Burning in excess air, the heavier alkali metals form superoxides,

MO X_{2}

. Rubidium does exactly this, giving

RbO X_{2}

, and when the superoxide meets water it hydrolyses to the hydroxide while releasing both hydrogen peroxide and oxygen:

2 RbO X_{2} + 2 H X_{2} O 2 RbOH + H X_{2} O X_{2} + O X_{2}

. The metal that behaves this way is rubidium.

JEE Main · 2019 · 12 Jan 2019 · Shift 1 · Single correct option