The vapour pressure of pure liquid A at 300K is 577 Torr and that of pure liquid B is 390 Torr. These two compounds form ideal liquid and gaseous mixtures. Consider the equilibrium composition of a mixture in which the mole fraction of A in the vapour is 0.35. Calculate the total pressure of the vapour and the composition of the liquid mixture.

The vapour pressure of pure liquid A at 300K is 577 Torr and that of p

1.	The vapour pressure of pure liquid A at 300K is 577 Torr and that of pure liquid B is 390 Torr. These two compounds form ideal liquid and gaseous mixtures. Consider the equilibrium composition of a mixture in which the mole fraction of A in the vapour is 0.35. Calculate the total pressure of the vapour and the composition of the liquid mixture.
Answer» <P> Solution :A and B volatile liquids, given `P_(A^(0)=575` Torr, `P_(B^(0)=390` Torr let mole fraction of `A` in solution `=X_(A)` HENCE, `P_("total")=P_(A^(0)X_(A)+P_(B)^(0)(1-X_(A))` also `X_(A)=` ,p,e fraction of A in the vapour `=0.35` `X_(A)=(P_(A)^(@)X_(A))/(P_(A)^(@)X_(A)+P_(B)^(@)(1-X_(A))=0.35` `=(575X_(A))/(575X_(A)+390(1-X_(A))` this GIVES `X_(A)=0.27` hence, total pressure `P_("total")=575xx0.27+390xx0.73` `=440` Torr Composition of liquid MIXTURE, `A=27` mol `%,B=73` mol `%` total pressure `=440` Torr