Chapter 13, Problem 13.71P

Departures from Raoult's law are primarily from liquid-phase nonidealities ( ${\gamma }_i\ne 1$ ).

But vapor-phase nonidealities ( ${\hat{\varphi }}_i\ne 1$ ) also contribute. Consider the special case where the liquid phase is an ideal solution, and the vapor phase a nonideal gas mixture described by Eq. (3.36). Show that departures from Raoult's law at constant temperature are likely to be negative. State clearly any assumptions and approximations.