9. Calculate the number of moles of each ion in solution when 12.0 g of sodium sulfate is dissolved in water.

I've been stuck on this question for an hour :( Can't figure out where I'm going wrong. Please show at least some of the solving process. I started off by converting 12 g of sodium sulfate into moles. Is that the correct first step even? Maybe that's where I'm going wrong. Thanks!

You started out correctly.

12.0 g Na2SO4 x (1 mole Na2SO4 / 142 g Na2SO4) = 0.0845 moles Na2SO4.

1 mole of Na2SO4(s) dissolves in water to give 2 moles of Na(aq) and 1 mole of SO4 2-(aq).

0.0845 moles Na2SO4 x (2 moles Na+ / 1 mole Na2SO4) = 0.169 moles Na+(aq)
0.0845 moles Na2SO4 x (1 mole SO4 2- / 1 mole Na2SO4) = 0.0845 moles SO4 2-(aq)