A mixture of 100 m mol of $\mathrm{Ca}(\mathrm{OH})_2$ and 2 g of sodium sulphate was dissolved in water and the volume was made up to 100 mL . The mass of calcium sulphate formed and the concentration of $\mathrm{OH}^{-}$in resulting solution, respectively, are (Molar mass of $\mathrm{Ca}(\mathrm{OH})_2, \mathrm{Na}_2 \mathrm{SO}_4$ and $\mathrm{CaSO}_4$ are 74,143 and $136 \mathrm{~g} \mathrm{~mol}^{-1}$, respectively; $\mathrm{K}_{\mathrm{sp}}$ of $\mathrm{Ca}(\mathrm{OH})_2$ is $5.5 \times 10^{-6}$ )