Which of the following salts is $NOT$ derived from a weak acid and a weak base?

Which of the following salts when dissolved in water will get hydrolysed?

If the $pK_b$ for $CN^-$ is $4.7$ at $25\,^oC$,then the $pH$ of a $0.5\,M \,NaCN$ solution is:

What happens when $CuSO_4$ is dissolved in water? Identify the correct statement from the following:

$A$ weak acid $HX$ $(K_a = 10^{-5})$ on reaction with $NaOH$ gives $NaX$. For $0.1 \ M$ aqueous solution of $NaX$,the $\%$ hydrolysis is $....... \ \%$.

$A$ salt is formed from a weak acid and a weak base. If $pK_b > pK_a$,then the $pH$ of the aqueous solution is $.....$