Answer: Calcium, magnesium and iron
Notes: Hard water is surface or under ground water that has high mineral content. In domestic settings, hard water is often indicated by a lack of froth formation when soap is agitated in water. Wherever water hardness is a concern, water softening is commonly used to reduce hard water’s adverse effects. Usually, the cations have the charge of 2+. The metallic constituents of hard water are mostly Calcium, magnesium and iron. Therefore, washing soda (Na2CO3.10H2O) is used to remove hardness. The sodium ions easily replace those cations responsible for hardness of water.
