$A$ $0.1 \ N$ solution of an acid at room temperature has a degree of ionisation $0.1$. The concentration of $OH^{-}$ would be

In which case is the change in $pH$ maximum?

$A$ weak acid is titrated with a weak base. Consider the following statements regarding the $pH$ of the solution at the equivalence point.
$(i)$ $pH$ depends on the concentration of acid and base
$(ii)$ $pH$ is independent of the concentration of acid and base
$(iii)$ $pH$ depends on the $pK_{a}$ of acid and $pK_{b}$ of base
$(iv)$ $pH$ is independent of the $pK_{a}$ of acid and $pK_{b}$ of base
The correct statements are

The $pH$ of the solution formed by mixing $5 \ mL$ of $M/5$ $HCl$ and $10 \ mL$ of $M/10$ $NaOH$ is:

The plot of $pH$-metric titration of weak base $NH_4OH$ vs strong acid $HCl$ looks like:

The hydrogen ion concentration in a mixture of $10 \ mL$ of $0.1 \ M$ $H_2SO_4$ and $10 \ mL$ of $0.1 \ M$ $KOH$ solution in water,is . . . . . . $M$.