A students wants to change soft water into hard water . for this he should
a) add a pinch of sodium chloride in it
b)add a pinch of washing soda in it
c)add a pinch of calcium sulphate or magnesium sulphate in it
d) all of the above

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Solution

Hard water contains divalent calcium and magnesium ions. So if CaSO₄ or MgSO₄ is added to water it will become hard.
Hence option c) is the answer.

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Similar questions

Q. A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory there are some salts, which when dissolved in distilled water can convert it into hard water. Select from the following groups of salts, which when dissolved in distilled water will make it hard.
(a) Sodium chloride, Potassium chloride
(b) Sodium sulphate, Potassium sulphate
(c) Sodium sulphate, Calcium sulphate
(d) Calcium sulphate, Magnesium chloride

Q. Assertion :Permanent hardness of water can be removed by using washing soda Reason: Washing soda reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates

Assertion (A): Permanent hardness of water is removed by treatment with washing soda.
Reason(R): Washing soda reacts with soluble magnesium and calcium sulphate to form water-soluble compounds.

Select from the following group of these salts which may be dissolved in water to make it hard.

(I) Sodium chloride
(II) Sodium sulphate
(III) Calcium chloride
(IV) Calcium sulphate
(V) Potassium chloride
(VI) Magnesium sulphate

Q. Hard water required for an experiment is not available in a school laboratory. However, the following salts are available in the laboratory. Select the salts which may be dissolved in water to make it hard for the experiment :

(1) calcium sulphate
(2) sodium sulphate
(3) calcium chloride
(4) potassium sulphate
(5) sodium hydrogen carbonate
(6) magnesium chloride

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A students wants to change soft water into hard water . for this he shoulda) add a pinch of sodium chloride in itb)add a pinch of washing soda in itc)add a pinch of calcium sulphate or magnesium sulphate in itd) all of the above

Hard water contains divalent calcium and magnesium ions. So if CaSO4 or MgSO4 is added to water it will become hard. Hence option c) is the answer.

A students wants to change soft water into hard water . for this he should
a) add a pinch of sodium chloride in it
b)add a pinch of washing soda in it
c)add a pinch of calcium sulphate or magnesium sulphate in it
d) all of the above

Hard water contains divalent calcium and magnesium ions. So if CaSO₄ or MgSO₄ is added to water it will become hard.
Hence option c) is the answer.