$15\mathrm{.}4.$ In a binary solution of two components, the eutectic point is the lowest freezing point of

the mixture. It is less than the freezing point of either pure component.

Assume that the liquid phase forms an ideal solution and that all solid phases are pure

components $($i$.$e$.,$ no mixed crystals form$).$ The vapor phase forms an ideal$-$gas mixture.

Some data that may be of use are given below. Neglect any pressure effects. Assume that

$H$ values do not vary witb temperature.

Estimate the eutectic point $($i$.$e$.,$ composition and temperature$)$ for a liquid$-$air mixture

and $\{$:$N_2).$