Question

A solution is prepared by mixing 25.0 g H2O and 25.0 g C2H5OH. Determine the mole fractions of each substance.

Answer 1

Answer:

Mole fraction H₂O → 0.72

Mole fraction C₂H₅OH → 0.28

Explanation:

By the mass of the two elements in the solution, we determine the moles of each:

25 g . 1 mol/ 18g = 1.39 moles of water (solute)

25 g . 1 mol / 46 g = 0.543 moles of ethanol (solvent)

Mole fraction solute = Moles of solute / Total moles

Mole fraction solvent = Moles of solvent / Total moles

Total moles = Moles of solute + Moles of solvent

1.39 moles of solute + 0.543 moles of solvent = 1.933 moles → Total moles

Mole fraction H₂O = 1.39 / 1.933 → 0.72

Mole fraction C₂H₅OH= 0.543 / 1.933 → 0.28

Remember that sum of mole fractions = 1

Answer 2

Answer:

Mol fraction H2O = 0.72

Mol fraction C2H5OH = 0.28 moles

Explanation:

Step 1: Data given

Mass of H2O = 25.0 grams

Molar mass H2O = 18.02 g/mol

Mass of C2H5OH = 25.0 grams

Molar mass C2H5OH = 46.07 g/mol

Step 2: Calculate moles

Moles = mass / molar mass

Moles H2O = 25.0 grams / 18.02 g/mol

Moles H2O = 1.39 moles

Moles C2H5OH = 25.0 grams / 46.07 g/mol

Moles C2H5OH = 0.54 moles

Step 3: Calculate total moles

Total moles = 1.39 moles + 0.54 moles

Total moles = 1.93 moles

Step 4: Calculate mol fractions

Mol fraction = moles / total moles

Mol fraction H2O = 1.39 moles / 1.93 moles

Mol fraction H2O = 0.72

Mol fraction C2H5OH = 0.54 moles / 1.93 moles

Mol fraction C2H5OH = 0.28 moles