What will be the $pH$ of a $0.1 \ M$ $NH_3$ solution?

At $298 \ K$ temperature,calculate the $pH$ of a $0.25 \ M$ solution of $(CH_3)_2NH$ given that its $K_b$ is $5.4 \times 10^{-4}$.

The $pH$ of $0.004 \, M$ hydrazine solution is $9.7$. Calculate its ionization constant $K_{b}$ and $pK_{b}$.

The $pH$ of a $1.0 \ M$ monobasic acid $HX$ is $2$. The van't Hoff factor for the aqueous solution of the acid will be ........

Consider the dissociation equilibrium of the following weak acid $HA \rightleftharpoons H^{+}_{(aq)} + A^{-}_{(aq)}$. If the $pK_{a}$ of the acid is $4$,then the $pH$ of $10 \ mM$ $HA$ solution is . . . . . . . (Nearest integer)
[Given : The degree of dissociation can be neglected with respect to unity]

At $T$ $(K)$,if the ionisation constant of ammonia in solution is $2.5 \times 10^{-5}$,the $pH$ of $0.01 \ M$ ammonia solution and the ionisation constant of its conjugate acid respectively at that temperature are $(\log 2 = 0.30)$