A 3.0 molal NaOH solution has a density of 1.12 g/mL. What is the percentage w/v of the solution? (Atomic masses: Na = 23, H = 1, O = 16)

2.97
3
12
3.5

Correct answer: 12

Solution

3 molal: 3 mol NaOH dissolved in 1000 g water. Mass of NaOH = 3*40 = 120 g. Total solution mass = 1000+120 = 1120 g. Volume of solution = 1120 g / 1.12 g/mL = 1000 mL. % w/v = 120 g / 1000 mL * 100 = 12%.

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