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An aqueous KOH solution is 7.0 M and contains 28% KOH by mass. Calculate the density of the solution in g/mL. (Molar mass of KOH = 56, K = 39.)

1. 1.40 g/mL
2. 1.20 g/mL
3. 1.00 g/mL
4. 1.56 g/mL

Correct answer: 1.40 g/mL

Solution

Using M = 10 * (mass%) * d / molar mass, solve for d: d = 7 * 56 / (10 * 28) = 392/280 = 1.40 g/mL.

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