Given three solvents X, Y, Z. Order of boiling point of pure solvent X < Y < Z and same order of molal elevation constant ($K_\mathrm{b}$). Find the order of molecular mass.

So I got this question in my tuition test and the solution is unclear. This question is troubling me a lot.


I can see how this question is troubling.

It don't think there is a solution.

$K_b = \frac{RT_b^2M_w}{1000\Delta H_v}$

Where $T_b$ is boiling point, $\Delta H_v$ is the molar heat of vaporization, and $M_w$ is molecular weight of the solvent.

(see Colligative Properties by W. R. Salzman)

So you can see that knowing $K_b$ and $T_b$ is insufficient to find $M_w$, knowledge of $\Delta H_v$ is also required.

Experimentally, from Table of cryoscopic and ebullioscopic constants you can also see there is no solution.


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