Question

What is the vapor pressure, in toor, of a solution formed by dissolving 0.500 moles of quinine in 1.50 moles of ethanol at 35 degrees C? The vapor pressure of pure ethanol is 100. toor at this temperature. assume ideal behavior.

A. 2.50x10^1

B. 5.00x10^1

C. 7.50x10^1

D.1.33x10^2

E. 1.50x10^2

Answer 1

Answer:

Given moles of quinine=0.5 mol,

moles of ethanol=1.5 mol.

Vapor pressure of pure ethanol=100 torr.

According to Raoult's law,

P_solution = (χ_solvent) (P°_solvent)

P_solution =vapor pressure of the solution,

χ_solvent=mole fraction of solvent=moles of solvent/total moles of solution

P°_solvent=vapor pressure of the pure solvent.

Here solvent is ethanol.

Total moles of solution=moles of quinie + moles of ethanol=0.5 mol + 1.5 mol=2 mol

χ_solvent=(1.5 mol)/(2 mol)=0.75.

P°_solvent=100 torr.

Therefore P_solution = (χ_solvent) (P°_solvent)=0.75 x 100 torr=75 torr.

Therefore vapor pressure of solution=7.5 x 10^1.

Option (C) is correct.

Please let me know if you have any doubt. Thanks.