Assign $A, B, C, D$ from the given type of reaction.
$BaCO_3 \downarrow + CO_2 + H_2O \longrightarrow Ba(HCO_3)_2$

The number of hydroxyl ions in $10 \text{ cm}^3$ of $0.2 \text{ M}$ $HCl$ solution is

Which one of the following statements is correct?

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: $K_a = 5 \times 10^{-4}, pK_a = 3.3, \alpha << 1$

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 .......

The solubility product of a sparingly soluble salt $A_{2}X_{3}$ is $1.1 \times 10^{-23}$. If specific conductance of the solution is $3 \times 10^{-5} \ S \ m^{-1}$,the limiting molar conductivity of the solution is $x \times 10^{-3} \ S \ m^{2} \ mol^{-1}$. The value of $x$ is ...