What is the pH of 10 L of a buffer solution containing $0.01 \mathrm{M} \mathrm{NH}_4 \mathrm{Cl}$ and $0.1 \mathrm{M} \mathrm{NH}_4 \mathrm{OH}$ having $\mathrm{pK}_b$ of 5 ?

Calculate the molar solubility of calcium hydroxide $\mathrm{Ca}(\mathrm{OH})_2$ in 0.10 M NaOH solution. The ionic product of calcium hydroxide is $5.5 \times 10^{-6}$.

Match the given ionisation constant values with the corresponding acids.

$$ \begin{array}{lll} \hline \text { A. } & \mathrm{HI} & \text { (i) } 3.2 \times 10^9 \\ \hline \text { B. } & \mathrm{HF} & \text { (ii) } 3.5 \times 10^{-4} \\ \hline \text { C. } & \mathrm{HCl} & \text { (iii) } 1.3 \times 10^6 \\ \hline \text { D. } & \mathrm{HBr} & \text { (iv) } 1.0 \times 10^9 \\ \hline \end{array} $$

$$ \text { The correct match is } $$