Calculate the solubility product of sparingly soluble salt BA at $25^{\circ} \mathrm{C}$ if its solubility is $7.2 \times 10^{-7} \mathrm{~mol} \mathrm{~dm}^{-3}$ at same temperature.

Calculate the $[\mathrm{OH}]$ if pOH of solution is 4.94

Which from following mixtures in water acts as a basic buffer?

Calculate the pH of a buffer solution containing 0.35 M weak acid and 0.70 M of its salt with strong base if $\mathrm{pK}_{\mathrm{a}}$ is 4.56 .