What is $[{H^ + }]$ of a solution that is $0.01\,M$ in $HCN$ and $0.02\,M$ in $NaCN$ $({K_a}$for $HCN = 6.2 \times {10^{ - 10}})$

$K _{ a_1,}, K _{ a_2 }$ and $K _{ a_3}$ are the respective ionization constants for the following reactions $(a), (b),$ and $(c)$.

$(a)$ $H _{2} C _{2} O _{4} \rightleftharpoons H ^{+}+ HC _{2} O _{4}^{-}$

$(b)$ $HC _{2} O _{4}^{-} \rightleftharpoons H ^{+}+ HC _{2} O _{4}^{2-}$

$(c)$ $H _{2} C _{2} O _{4} \rightleftharpoons 2 H ^{+}+ C _{2} O _{4}^{2-}$

The relationship between $K_{a_{1}}, K_{ a _{2}}$ and $K_{ a _{3}}$ is given as

Calculate $pH$ of solution of $6.0$ $gm$ acetic acid in $250$ $mL$. ( ${K_a} = 1.8 \times {10^{ - 5}}$ at $298$ $K$ ) ( $C = 12, H = 1, O = 16$ )

Calculate the $pH$ of the solution in which $0.2 \,M\, NH _{4} Cl$ and $0.1 \,M\, NH _{3}$ are present. The  $pK _{ b }$ of ammonia solution is $4.75$

A solution of sodium borate has a $pH$ of approximately

If $pK_a =\, -\,log K_a=4$ for a weak acid $HX$ and $K_a= C\alpha ^2$ then Van't Haff factor when $C = 0.01\,M$ is