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10.30 mg of O2 is dissolved in one litre of sea water whose density is 1.03 g/mL. Express the O2 concentration in ppm (by mass).

1. 10 ppm
2. 5 ppm
3. 1 ppm
4. 100 ppm

Correct answer: 10 ppm

Solution

Mass of solution = 1000*1.03 = 1030 g. ppm = (10.30e-3 g / 1030 g)*10⁶ = 10 ppm.

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