Question

Why do soaps not work in hard water?

Answer 1

Soap is less effective in hard water since it reacts to form a calcium or magnesium salt of the organic acid in the soap

Answer 2

The soap is made up of the long chain of fatty acids that are added up with the potassium or sodium whereas hard water will have the magnesium and calcium ions.

When we work out soap with hard water then the ions will displace the potassium or calcium from salts.

This turns out to be the insoluble magnesium or calcium salts making it scum.