(i) Statements A and R both are correct and R is the correct explanation of A.
Permanent hardness of water is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphates in water.
Permanent hardness can be removed by treatment of water with washing soda which contains sodium carbonate. Washing soda reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates.
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