The plot given below shows P-T curves (where | vedclass

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(B) From the graph,the boiling points of pure solvents $X$ and $Y$ are $360 \ K$ and $367 \ K$ respectively,and for their $NaCl$ solutions are $362 \

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$0.05$

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(B) From the graph,the boiling points of pure solvents $X$ and $Y$ are $360 \ K$ and $367 \ K$ respectively,and for their $NaCl$ solutions are $362 \ K$ and $368 \ K$ respectively.For $NaCl$ (completely dissociated,$i = 2$):$(\Delta T_b)_X = i (K_b)_X m = 362 - 360 = 2 \ K$$(\Delta T_b)_Y = i (K_b)_Y m = 368 - 367 = 1 \ K$Dividing the two equations: $\frac{(K_b)_X}{(K_b)_Y} = \frac{2}{1} = 2$.For solute $S$ undergoing dimerization,the Van't Hoff factor is $i = 1 - \frac{\alpha}{2}$.Given $\alpha_Y = 0.7$,so $i_Y = 1 - \frac{0.7}{2} = 0.65$.Given $(\Delta T_b)_X = 3 (\Delta T_b)_Y$ for solute $S$:$i_X (K_b)_X m = 3 \cdot i_Y (K_b)_Y m$$(1 - \frac{\alpha_X}{2}) \cdot (K_b)_X = 3 \cdot (0.65) \cdot (K_b)_Y$$(1 - \frac{\alpha_X}{2}) \cdot 2 = 1.95$$1 - \frac{\alpha_X}{2} = 0.975$$\frac{\alpha_X}{2} = 0.025$$\alpha_X = 0.05$.

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