What will be the $pH$ of a solution formed by mixing $40 \, cm^3$ of $0.1 \, M \, HCl$ with $10 \, cm^3$ of $0.45 \, M \, NaOH$?

Calculate the ionic product of the solution formed by mixing equal volumes of $0.004 \, M \, CaSO_4$ and $0.002 \, M \, H_2SO_4$.

In which of the following mixed aqueous solutions,$pH = pK_{a}$ at equilibrium?
$(1)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ CH_{3}COONa$
$(2)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 50 \ mL$ of $0.1 \ M \ NaOH$
$(3)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NaOH$
$(4)$ $100 \ mL$ of $0.1 \ M \ CH_{3}COOH + 100 \ mL$ of $0.1 \ M \ NH_{3}$

For a $C \ M$ solution of a weak base $BOH$ having a van't Hoff factor '$i$',the base dissociation constant $K_b$ will be:

For a $0.01 \ M \ HCN$ solution,the van't Hoff factor is $1.002$. What will be the acid dissociation constant $(K_a)$ for $HCN$?

$CrO_4^{2-}$ (yellow) changes to $Cr_2O_7^{2-}$ (orange) in $pH = x$ and vice-versa in $pH = y$. Hence,$x$ and $y$ are