Oops, I accidently posted this as an answer to my previous question, when in fact it was another question.
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How do I convert mg/L NaCl to mg/L Na^+?
What I tried was:
ppm Na^+ = mg/L Na^+ = 1mg NaCl/L * (22.99gNa/35.45gCl) = 0.649 ppm Na^+
But this didn't seem right to me... I feel like I am missing something...
answered below.