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For a 100 molal aqueous solution, the mole fraction of the solute is approximately ___ x 10⁻² (rounded to the nearest integer). [H = 1.0 u, O = 16.0 u]

1. 64
2. 50
3. 36
4. 18

Correct answer: 64

Solution

With 100 mol solute and 1000/18 = 55.56 mol water, the solute mole fraction is 100/155.56 = 0.643, i.e. about 64 x 10⁻².

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