Question: how many moles of sodium ions are there in 1 mole of sodium carbonate?
Answer: 4 grams/(105.99g/mol)=0.03774mol Sodium Carbonate in 1 L, meaning 0.03774 M. For every 1 mole of CO3, we have 2 moles of Na. Using our moles of Na2CO3, we know we have 2*0.03774 mol of sodium from sodium carbonate.