Question

Which one of the following compounds is a peroxide?

• A. $BaO_2$
• B. $MnO_2$
• C. $NO_2$
• D. $KO_2$

Answer 1

Answer: (A)

$BaO_2$

Answer 2

In peroxide the oxidation number of $0$ is $-1$ and they give $H_2O_2$ with dilute acids and have peroxide linkage. In $KO_2$ let O.S. of $O = x$ $\therefore$ $1 + (x \times 2) = 0$ $\therefore = 1/2$ (It is a superoxide, not a peroxide). In $BaO_2$, let $O.S.$ of $O = x$ $2 + (x \times 2) = 0$ $\therefore \, x = - 1$(It is a peroxide) In $MnO_2$ and $NO_2$, $Mn$ 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 $BaO_2$ is a peroxide.