Order of molecular mass of solvent; given boiling point [closed]








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> 
> 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.
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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](http://www.chem.arizona.edu/~salzmanr/480a/480ants/colprop/colprop.html))


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](http://www.vaxasoftware.com/doc_eduen/qui/tcriosebu.pdf) you can also see there is no solution. 


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