The vapour pressure of pure benzene and methyl benzene at 27°C is given as 80 Torr and 24 Torr, respectively. The mole fraction of methyl benzene in vapour phase, in equilibrium with an equimolar mixt

Question

The vapour pressure of pure benzene and methyl benzene at 27°C is given as 80 Torr and 24 Torr, respectively. The mole fraction of methyl benzene in vapour phase, in equilibrium with an equimolar mixture of those two liquids (ideal solution) at the same temperature is  (nearest integer)

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Strategy:
 For an ideal solution, the vapor phase mole fraction () is given by its partial pressure divided by the total pressure. Use Raoult's Law to find the partial pressures.

Step 1: Partial pressures for equimolar mixture ()
- 
-

Step 2: Total vapor pressure
.

Step 3: Vapor phase mole fraction of methyl benzene (toluene)

Nearest integer = 23.

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