The molality of an unknown aqueous solution was found to be 3.50 m . What is the mole fraction of water (molar mass = 18.0 g/mol) in this solution?

Question

Quizplus · Accepted Answer

The mole fraction of water in the solution can be calculated using the definition of molality and the mole fraction formula. Molality (m) is defined as the number of moles of solute per kilogram of solvent. Given a molality of 3.50 m, this means there are 3.50 moles of solute per 1 kg (1000 g) of water. The molar mass of water is 18.0 g/mol, so the number of moles of water in 1 kg is 1000 g / 18.0 g/mol = 55.56 moles. The mole fraction of water (X_water) is then the number of moles of water divided by the total number of moles (moles of water + moles of solute): X_water = 55.56 / (55.56 + 3.50) = 55.56 / 59.06 ≈ 0.941.

The Molality of an Unknown Aqueous Solution Was Found to Be