Question

Which one of the following compounds is a peroxide?

• A. $Ba{O}_2$
• B. $Mn{O}_2$
• C. $N{O}_2$
• D. $K{O}_2$

Answer 1

Answer: (A)

In peroxide the oxidation number of $0$ is $-1$ and they give $H_2{O}_2$ with dilute acids and have peroxide linkage.
In $K{O}_2$ let O.S. of $O=x$
$\therefore$ $1+(x\times 2)=0$
$\therefore =1/2$ (It is a superoxide, not a peroxide).
In $Ba{O}_2$, let $O.S.$ of $O=x$
$2+(x\times 2)=0$
$\therefore x=-1$(It is a peroxide)
In $Mn{O}_2$ and $N{O}_2$, $Mn$ and $N$ exhibit variable oxidation states, the oxidation state of $0$ in these oxides is $-2$ and hence they are not peroxides. Among then only $Ba{O}_2$ is a peroxide.