$0.1 \ M$ solution of which of the following has almost unity degree of dissociation?

$A$ certain weak base has a dissociation constant $2 \times 10^{-5}$. The equilibrium constant for its neutralization reaction with a strong acid is

The first and second dissociation constants of a diprotic acid ${H_2}A$ are $1.0 \times 10^{-5}$ and $5.0 \times 10^{-10}$ respectively. The overall dissociation constant of the acid ${H_2}A$ is .......

When a standard solution of $NaOH$ is left in the air for a few hours,

For the equilibrium $2H_2O \rightleftharpoons H_3O^{+} + OH^{-}$,the value of $\Delta G^o$ at $298 \ K$ is approximately ....... $kJ \ mol^{-1}$.

At $25^{\circ}C$,$20.0 \ mL$ of $0.2 \ M$ weak monoprotic acid $HX$ is titrated against $0.2 \ M$ $NaOH$. The $pH$ of the solution $(a)$ at the start of the titration (when $NaOH$ has not been added) and $(b)$ when $10 \ mL$ of $NaOH$ is added respectively,are:
Given: $K_a = 5 \times 10^{-4}, pK_a = 3.3, \alpha << 1$