The solubility product of a sparingly soluble $A B_2$ salt is $2.56 \times 10^{-4} \mathrm{M}^3$ at $25^{\circ} \mathrm{C}$. The $K_f$ of water is 1.8 K kg mol ${ }^{-1}$. The depression in freezing point of a standard solution of $A B_2$ is

The observed molar mass determined for $\mathrm{Na}_2 \mathrm{SO}_4$ by freezing point depression method is $50.0 \mathrm{~g} / \mathrm{mol}$. The molecular weight of $\mathrm{Na}_2 \mathrm{SO}_4$ is 142 . What will be the degree of dissociation $\alpha$ for $\mathrm{Na}_2 \mathrm{SO}_4$ in water?

A 1.17 % solution of solute $A$ is isotonic with 7.2 % solution of glucose. If the molecular weight of solute $A$ is 58.5, the value of van't Hoff factor, ' $i$ ' is

A mixture of 3.0 moles of $\mathrm{Na}_2 \mathrm{O}$ and 1.5 mol of $\mathrm{KO}_2$ is dissolved in 1000 mL of water. The vapour pressure of the solution in Torr, at $100^{\circ} \mathrm{C}$ is