A mixture of ethyl alcohol and propyl alcohol has a vapour pressure

• Solutions

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

1. 300
2. 350
3. 360
4. 700

Answer

According to Raoult’s law,

P = P_A + P_B = P_A^o x_A + P_B^o x_B

290 = P_A^o (0.6) + 200 x (1-0.6)

P_A^o = 350 mm

The correct option is B.