An equilibrium liquid mixture of benzene and toluene is in equilibrium with its vapour at 30ºC. Using Raoult's law calculate Psystem and composition of vapour. YAPsys=XAP*A What we want to know is:
YA and Psys 1.- First at all we have to calculate P* for each component (benzene and toluene) Pb*=10^(A+(B/C+T)=10^(6.89272+(1203.531/30+219.888)=119 mmHg PT*=10^(A+(B/C+T)=10^(6.95805+(1346.773/30+219.693)=36.7 mmHg For the partial pressure benzene and toluene we multiply P* for the number of moles. The problem does not give that information but we assume we have 1 mol in total and they are in equilibrium so we can say that Benzene=0.5 mol and Toluene=0.5 mol Pb=119 mmHg (0.5 mol) = 59.5 mmHg*mol PT= 36.7 mmHg (0.5 mol) =18.35 mmHg*mol Psys = 59.5 mmHg*mol + 18.35 mmHg*mol=77.9 mmHg We have the total pression of the system! Now for the vapour composition we have to clear Yb and YT YAPsys=XAP*A ------- YA=XAP*A /Psys Yb=59.5 mmHg*mol/77.9 mmHg = 0.7637 mol benzene YT=18.35 mmHg*mol/77.9 mmHg = 0.2355 mol toluene