Describe what hard water is and how a water softening unit works. Provide balanced chemical equations to show how sodium sulphate can remove these ions (Magnesium and Calcium).

The first was no problem, but I am having trouble trying to get through the second part balancing chemical equations. I think that the chemical formula for sodium sulphate is Na2SO4 however I don't know where to go from there.

Any help you can give me would be so great! Thanks

1 answer

What happens is that the Na of Na2SO4 (many products use NaCl instead of Na2SO4) to replace the Ca, Mg, and other ions such as Fe. In simple fashion, if we let the resin be x, then
NaX + Ca^+2 ==> CaX2 + 2Na^+.
Mg and Fe would look the same.
Here is a Wikepedia article you can read if you need more information.
http://en.wikipedia.org/wiki/Water_softening