Problem: 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?

FREE Expert Solution

We are asked to determine the number of moles of Na+ needed to replace Ca2+ and Mg2+.


In order for us to solve this problem, we shall follow these steps:

Step 1: Determine the number of moles of each Ca2+ and Mg2+ using the volume of hard water.

Step 2: Perform a mole-to-mole comparison (1 mol Ca2+:2 mol charge and 1 Mg2+:2 mol charge).

Step 3: Get the total mole charge and perform a mole-to-mole comparison with Na+ ion (1 mol charge: 1 mol Na+).


We can use this similar video at Clutch as a guide:

https://www.clutchprep.com/chemistry/practice-problems/69290/hard-water-contains-ca2-mg2-and-fe2-which-interfere-with-the-action-of-soap-and-

View Complete Written Solution
Problem Details

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?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Solubility Rules concept. You can view video lessons to learn Solubility Rules. Or if you need more Solubility Rules practice, you can also practice Solubility Rules practice problems.