(a) (i) Why is boiling point of $$1 \mathrm{~M} \mathrm{~NaCl}$$ solution more than that of $$1 \mathrm{M}$$ glucose solution?

(ii) A nonvolatile solute '$$\mathrm{X}$$' (molar mass $$=\mathbf{5 0} \mathrm{~g} \mathrm{~mol}^{-1}$$) when dissolved in $$78 \mathrm{~g}$$ of benzene reduced its vapour pressure to $$90 \%$$.

Calculate the mass of $$\mathrm{X}$$ dissolved in the solution.

(iii) Calculate the boiling point elevation for a solution prepared by adding $$10 \mathrm{~g}$$ of $$\mathrm{MgCl}_2$$ to $$200 \mathrm{~g}$$ of water assuming $$\mathrm{MgCl}_2$$ is completely dissociated.

($$\mathrm{K}_{\mathrm{b}}$$ for Water $$=0.512 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$$, Molar mass $$\mathrm{MgCl}_2=95 \mathrm{~g} \mathrm{~mol}^{-1}$$)

OR

(b) (i) Why is the value of Van't Hoff factor for ethanoic acid in benzene close to 0.5 ?

(ii) Determine the osmotic pressure of a solution prepared by dissolving $$2.32 \times 10^{-2} \mathrm{~g}$$ of $$\mathrm{K}_2 \mathrm{SO}_4$$ in $$2 \mathrm{~L}$$ of solution at $$25^{\circ} \mathrm{C}$$, assuming that $$\mathrm{K}_2 \mathrm{SO}_4$$ is completely dissociated.

($$\mathrm{R}=0.082 \mathrm{~L} \mathrm{~atm} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$$, Molar mass $$\mathrm{K}_2 \mathrm{SO}_4 =174 \mathrm{~g} \mathrm{~mol}^{-1}$$)

(iii) When $$25.6 \mathrm{~g}$$ of sulphur was dissolved in $$1000 \mathrm{~g}$$ of benzene, the freezing point lowered by $$0.512 \mathrm{~K}$$. Calculate the formula of sulphur ($$\mathrm{S}_{\mathrm{x}}$$). ($$\mathrm{K}_{\mathrm{f}}$$ for benzene $$=5.12 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$$, Atomic mass of Sulphur $$=32 \mathrm{~g} \mathrm{~mol}^{-1}$$ )