Benzene (${\mathrm{C}}_6{\mathrm{H}}_6$, 78 g/mol) and toluene (${\mathrm{C}}_7{\mathrm{H}}_8$, 92 g/mol) form an ideal solution. At ${60}^{o}C$ the vapour pressure of pure benzene and pure toluene are 0.507 atm and 0.184, respectively. The mole fraction of benzene in a solution of these two chemicals that has a vapour pressure of 0.350 atm at ${60}^{o}C$