Which one is a mixed salt?

$5 \ mL$ of $0.4 \ N$ $NaOH$ is mixed with $20 \ mL$ of $0.1 \ N$ $HCl$. The $pH$ of the resulting solution will be

$A$ $20 \ mL$ sample of a $0.1 \ M$ solution of the weak monoprotic acid $HA$ is titrated with $0.25 \ M \ NaOH$. The volume of $NaOH$ solution required to reach the equivalence point is: ............. $mL$

Estimate the approximate $pK_a$ of $0.5 \ M$ $CH_3COOH$. Degree of dissociation (ionisation) is $0.15$ $(\log 1.32 = 0.12)$.

Hydrogen ion concentration of an aqueous solution is $1 \times 10^{-4} \ M$. The solution is diluted with an equal volume of water. The hydroxyl ion concentration of the resultant solution in terms of $mol \ dm^{-3}$ is

What would happen when a solution of potassium chromate is treated with an excess of dilute nitric acid?