A solution was prepared by dissolving 23 grams of ethyl alcohol in a 56 grams of water. Calculate the volume percent and mole fraction of this solution.

Question

A solution was prepared by dissolving 23 grams of ethyl alcohol in a 56 grams of water. Calculate the volume percent and mole fraction of this solution.

Answer 1

molar mass ethyl alcohol (C₂H₅OH) = 46.1 g/mol

molar mass H₂O = 18 g/mol

mols ethyl alcohol = 23 g x 1 mol / 46.1 g = 0.50 mols

mols H₂O = 56 g x 1 mol / 18 g = 3.11 mols

total mols = 0.50 + 3.11 = 3.61

mol fraction ethyl alcohol = 0.51 mols / 3.61 mols = 0.139 = 0.14

mol fraction H₂O = 3.11 mols / 3.61 mols = 0.861 = 0.86

To find the % ethyl alcohol by volume, we would need to know the density of the final solution, which isn't given. Or we'd need the final volume and density of ethyl alcohol, neither of which is given. Perhaps, the question meant to ask the mass %, and not the volume %. In that case, the mass percent would be...

mass ethyl alcohol / mass of total solution (x100) = 23 g / (23 g + 56 g) = 23 / 79 (x100) = 29%