• # question_answer Hardness of water is due to presence of salts of [BHU 2005] A) $N{{a}^{+}}$ and ${{K}^{+}}$ B) $C{{a}^{2+}}$and $M{{g}^{2+}}$ C) $C{{a}^{2+}}$and ${{K}^{+}}$ D) $C{{a}^{2+}}$ and  $N{{a}^{+}}$

Hardness of water is due to the presence of bicarbonates, chlorides and sulphates of $Ca$ and $Mg$ on it. These $C{{a}^{2+}}$ and $M{{g}^{2+}}$ ions react with the anions of fatty acids present in soaps to form curdy white precipitates. As a result, hard water does not produce lather with soap immediately.