Which among the following salts turns red litmus blue in its aqueous solution?

The aqueous solution of $CH_3COONa$ is .......

Arrange the aqueous solutions of the following salts in the increasing order of their $pH$.
$I$. $CuSO_4$
$II$. $NaCN$
$III$. $KCl$

Calculate the $pH$ on mixing $100 \ mL$ of $0.2 \ M \ HCN$ with $400 \ mL$ of $0.05 \ M \ KOH$ at $25 \ ^\circ C$ ($pK_b$ for $CN^- = 8$).

Why is the following anionic hydrolysis correct?
$X^{-} + H_2O \rightleftharpoons HX + OH^{-}$

$20\,mL$ of $0.1\,M\,NH_{4}OH$ is mixed with $40\,mL$ of $0.05\,M\,HCl$. The $pH$ of the mixture is nearest to. (Given: $K_{b}(NH_{4}OH) = 1 \times 10^{-5}, \log 2 = 0.30, \log 3 = 0.48, \log 5 = 0.69, \log 7 = 0.84, \log 11 = 1.04$) (in $.2$)