Question -
Answer -
Soaps are sodium or potassium salts of long-chain fattyacids. Hard water contains calcium and magnesium ions. When soaps are dissolvedin hard water, these ions displace sodium or potassium from their salts andform insoluble calcium or magnesium salts of fatty acids. These insoluble saltsseparate as scum.
This is the reason why soaps do not work in hard water.