Which one of the following compounds is a peroxide?
Which one of the following compounds is a peroxide?
$\mathrm{KO}_2$
$\mathrm{BaO}_2$
$\mathrm{MnO}_2$
$\mathrm{NO}_2$
Solution
Key Idea:- In peroxides, the oxidation state of $O$ is - 1 and they give $\mathrm{H}_2 \mathrm{O}_2$, with dilute acids, and have peroxide linkage.
In $\mathrm{KO}_2$,
$+1+(\mathrm{x} \times 2)=0$
$x=-\frac{1}{2}$ (thus, it is a superoxide, not $a$ peroxide.)
In $\mathrm{BaO}_2$,
$\begin{aligned}
& +2+(\mathrm{x} \times 2)=0 \\
& \mathrm{x}=-1
\end{aligned}$
Thus, it is a peroxide. Only it gives $\mathrm{H}_2 \mathrm{O}_2$ when reacts with dilute acids and has peroxide linkage as
$\begin{aligned}
& \mathrm{Ba}^{2+}[\mathrm{O}-\mathrm{O}]^{2-} \\
& \text { peroxide linkage }
\end{aligned}$
In $\mathrm{MnO}_2$ and $\mathrm{NO}_2, \mathrm{Mn}$ and $\mathrm{N}$ exhibit variable oxidation states, thus, the oxidation state of $O$ in these is -2. Hence, these are not peroxides. Thus, it is clear, that among the given molecules only $\mathrm{BaO}_2$ is a peroxide.