Question: how many sodium ions are present in 30.0 ml of 0.600 m na2co3 solution?
Answer: 0.600mol/L * 1L/1000mL * 30.0mL = 0.018 moles of Na2CO3. There are 3 moles of ions (2 Na+ and 1 CO3-) for each moles of Na2CO3 in solution, so triple it!