Question

A solution of ethanol (C2H6O) in water is sometiems used as a disenfectant. 1.00 L of this solution contains 553 g of ethanol and 335 g of water. What is the mole fraction of ethanol in this solution? *show all work and calculations

Answer 1

Moles fraction = Moles solute / Total moles in solution

So, calculate the moles of solute (C₂H₅OH)

moles = mass / molar mass
molar mass C₂H₅OH = 46 g/mol
moles C₂H₅OH = 553 g / 46 g/mol
= 12.02 moles NaCl

And Calculate the moles of solvent,
mass solvent = 335 g

moles solvent = mass / molar mass
molar mass solvent = 18.0 g/mol
mass solvent = 335 g / 18.0 g/mol
= 18.61 mol solvent

Total number moles in solution = moles solute + moles solvent
= 12.02 mol + 18.61 mol
= 30.63 mol moles in solution

mole fration = moles solute / total moles in solution
= 12.02 mol / 30.63 mol
= 0.3924