Question

Which of the following is not a peroxide?

• A. $K{O}_2$
• B. $Cr{O}_5$
• C. $N{a}_2{O}_2$
• D. $Ba{O}_2$

Answer 1

The correct option is A $K{O}_2$

$K{O}_2$ is a superoxide $\left(K^{+}{O}_2^{-}\right)$, and the rest are peroxides $\left(O_2^{2-}\right)$.
In $Cr{O}_5$, $Cr$ is in $+6$ oxidation state, it contains two peroxide bonds.
In $N{a}_2{O}_2$, $Na$ is in $+1$ oxidation state as it contains peroxide linkage.
In $Ba{O}_2$, $Ba$ is in $+2$ oxidation state as it contains peroxide linkage.