# Problem: At 63.5˚C the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. What is the mole fraction of ethanol in the solution?

###### FREE Expert Solution

Mole Fraction (X) relates the moles of solute and solvent within a solution:

Assume the total mass is 100 g, so each would have to weigh 50 g.

molar mass ethanol
C2H5OH     2 C x 12.01 g/mol N = 24.02 g/mol
6 H x   1.01 g/mol H =   6.06 g/mol
1 O x 16.00 g/mol O = 16.00 g/mol
Total:
46.08 g/mol

85% (475 ratings) ###### Problem Details

At 63.5˚C the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. What is the mole fraction of ethanol in the solution?

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