Question

Arrange the above compounds in decreasing order of acidity.

Answer 1

The acidity order $I>III>II>IV$

$I$ is most acidic due to ortho effect and$I-M$ of $N{O}_2$ group $III$ is more acidic than $II$ because $-N{O}_2$ in $II$ only show $-I$ effect where as is $III-N{O}_2$ group show $-Iand-M$effect.