$15\mathrm{.}13.$ The International Critical Tables, Vol. III, p$.313,$ lists the boiling points for mixtures of

acetaldehyde and ethyl alcohol at various pressures. The data are summarized below for

mixtures containing $80$ mole$\%$ ethyl alcohol in the liquid.

From these data determine the molar enthalpy of vaporization of ethyl alcohol at $320\mathrm{.}7$

$K,$ from a liquid mixture containing $80\%$ ethyl alcohol. $[$That is$,$ what is $(\frac{?}{\text{b}\text{a}\text{r}}(H{)}^V\frac{-}{b}ar(H{)}^2)$

alcohol?$]$

Note: The vapor phase may be considered to be an ideal$-$gas mixture, but the liquid phase

is a non$-$ideal solution.