Question

In a locality, hard water, required for an experiment, is not available. However, the following salts are available in the school laboratory :
1. Sodium sulphate
2.Calcium sulphate
3. Magnesium chloride
4. Sodium chloride
5. Calcium chloride
6. Potassium sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment ?
(A) 2, 3 and 5     
(B)  1,2 and 5
(C) 1,2,4 and 6   
(D) 3 and 5 only

Answer 1

the answer is option (A) 2,3 and 5.

Answer 2

(A) 2,3 and 5

Permanent hardness is hardness that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium sulphate/calcium chloride and/or magnesium sulphate/magnesium chloride in the water, which do not precipitate out as the temperature increases.

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