I have a certain concentration of NaCl (in mg/L). I have to convert it to ppm Na+. I read some of the previous posts, and I understand that if I don't know the density, I should assume that 1ppm = 1mg/L.

Question

Does this also apply to ppm Na+ since there is 1 Na+ ion for each molecule NaCl. Or since it is in mg, do I have to find out how many mg Na there is in 1mg NaCl? How do I calculate this? I'm having a block... Do I need to use the molar mass?
Thanks.

You must convert mg/L NaCl to mg/L Na^+. And that many mg/L Na^+ will be ppm Na if it isn't too large a number (ppm and mg/L are not the same if the density is not 1.00 g/mL).

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...

almost.
1 mg NaCl*(Na/NaCl) = ??mg Na

Thanks!
(I feel so silly!)

don't. Asking questions is not silly. We don't learn if we don't ask.