Hard water contains Ca2+, Mg2+, and Fe2+, which interfere with the action of soap and leave an insoluble coating on the insides of containers and pipes when heated. Water softeners replace these ions with Na+. Keep in mind that charge balance must be maintained.
If 1600. L of hard water contains 0.021 M Ca2+ and 0.0050 M Mg2+, how many moles of Na+ is needed to replace these ions?