4. Benzene, C6H6, and toluene, C6H5CH3, form ideal solutions. At 35°C the vapor pressure of benzene is 160. torr and that of toluene is 50.0 torr. In an experiment, 3.9 mol of benzene and 5.7 mol of toluene are placed in a closed container at 35°C and allowed to come to equilibrium. What is the mole fraction of toluene in the vapor phase?