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An aqueous urea solution has a solute mole fraction of 0.2. Calculate the mass percent of urea in the solution. (Molar masses: urea = 60 g/mol, water = 18 g/mol)

1. 45.5%
2. 20.0%
3. 60.0%
4. 33.3%

Correct answer: 45.5%

Solution

0.2 mol urea = 12 g and 0.8 mol water = 14.4 g; mass percent = 12/26.4 * 100 = 45.5%.

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