Q. The correct order of acid strengths of benzoic acid $(X)$, peroxybenzoic acid $(Y)$ and $p$-nitrobenzoic acid $(Z)$ is

Solution:

$\because$ In $p$-nitrobenzoic acid $(Z)-N{O}_2$ present as electron withdrawing group, thus is most acidic

$(X)\because$ Benzoic acid is stabilised via resonance, thus is more acidic than per oxybenzoic acid.

$(Y)$ peroxy benzoic acid does not show any such resonance.

Thus is least acidic.
Hence, correct order is $Z>X>Y$.