Question

Which of the following group-$1$ metal forms majorly (mainly) the peroxide upon vigorous combustion in air ?

Answer 1

Group $1$ elements are also known as alkali metals.

These elements are very reactive & must be otred out of contact with air to prevent oxidation.

Reactivity increases as you go down the group; the less reactive metals $(Li,Na\&K)$ are strned in oil (thin coating of oil is sufficient to prevent reaction).

Metals like ($Rb$ & $Cs$) are stored in sealed gas tubes to eliminate contact with air.

Sodium $\left(Na\right)$ & Potassium $\left(K\right)$ are the two metals of group $1$ forms peroxide upon combustion in air.

Small pieces of sodium burn in air with a faint orange glow. The reaction produces a white solid mixture of sodium oxide & sodium peroxide.

$4Na+O_2\to 2N{a}_{2}O$

Peroxide equation:- $2Na+O_2\to N{a}_2{O}_2$

Small pices of potassium heated in air melt & convert instantly into a mixture & potassium peroxide & potassium superoxide without a visible a visible flame

Peroxide formation :- $2K+O_2\to K_2{O}_2$