2.38 Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at are and respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with toluene.
Firstly, we will find the no. of moles of the given compounds.
No. of moles of benzene :
and the no. of moles of toluene :
.
Now we will find mol fraction of both:-
Mole fraction of benzene :-
and mole fraction of toluene :
Now,
Ptotal = Pb + Pt
or
or
Hence mole fraction of benzene in vapour phase is given by :