A solution is made using 103.9 g of phenol (MM = 94.11 g/mol) and 70.0 g of acetone (MM = 58.08 g/mol). What is the mole fraction of the phenol in the solution?

Question

A solution is made using 103.9 g of phenol (MM = 94.11 g/mol) and 70.0 g of acetone (MM = 58.08 g/mol). What is the mole fraction of the phenol in the solution?

Answer 1

Hi Moh D.,

As you might suspect from the phrase "mole fraction", you are calculating a fraction, but doing it with moles of material, rather than by masses.

So use the data you are given, to convert each material's mass into a value for number of moles of it. Then add together the numbers of moles -- that sum is your denominator, and each material's number of moles is the numerator, for each mole fraction calculation. So for acetone, the calculation is: mass acetone/molar mass acetone = # moles acetone; mole fraction acetone = # moles acetone/ total # moles both materials.

-- Cheers, -- Mr. d.

P.S. Your mole fractions should add to 1. Did they?