Question

4mg of NaCl was weighed and topped up to 50ml.

Calculate the concentration of Na in ppm

Answer 1

$ppm = \frac{mass \;of\; Na^+}{mass\; of \;solvent} \times 10^6$

Proportion:

58.5 g NaCl contain 23 g Na⁺

$4 \times 10^{-3}$ g NaCl contain x g Na⁺

$x = \frac{4 \times 10^{-3} \times 23}{58.5}=1.57 \times 10^{-3} \;g \\ ppm = \frac{1.57 \times 10^{-3}}{50} \times 10^6 = 31.45 \;ppm$

Answer: 31.45 ppm