A litre of sea water weighing 1030 g contains about 6 x 10^-3 g of dissolved oxygen. The concentration of dissolved oxygen expressed in parts per million (ppm) by mass is approximately:

1. ppm (mass) = (mass of component / total mass) $\times 10^6$. 2. = $(6 \times 10^{-3} / 1030) \times 10^6$. 3. = $(5.83 \times 10^{-6}) \times 10^6$. 4. $\approx 5.8$ ppm. _Source: NCERT Class 12 Chemistry Ch 1 "Solutions", p.2_