A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of 290 mm at 300 K. The vapour pressure of propyl alcohol is 200 nm. If the mole fraction of ethyl alcohol is 0.6, its vapour pressure (in mm) at the same temperature will be
According to Raoult’s law,
P = PA + PB = PAo xA + PBo xB
290 = PAo (0.6) + 200 x (1-0.6)
PAo = 350 mm
The correct option is B.