Which of the following cannot be hydrolysed?

Calculate the hydrolysis constant $(K_h)$ for a salt containing $NO_2^-$. Given that the dissociation constant $(K_a)$ for $HNO_2$ is $4.5 \times 10^{-4}$ and the ionic product of water $(K_w)$ is $1.0 \times 10^{-14}$.

The $pH$ of ammonium phosphate solution,if $pK_a$ of phosphoric acid and $pK_b$ of ammonium hydroxide are $5.23$ and $4.75$ respectively,is ..... .

Calculate the percentage of hydrolysis in $0.01 \ M$ aqueous solution of $NaOCN$ ($K_b$ for $OCN^{-} = 10^{-10}$)

Which of the following salts does not undergo hydrolysis?

$A$ white salt is readily soluble in water and gives a colorless solution with a $pH$ of about $9$. The salt is ...........