Which of the following are true about hard water?

1.Hardness in water can occur in both surface and underground waters

2.Hardness increases the cleaning efficiency of water

3.It is caused by carbonates of magnesium and calcium

4.Hard water is considered safe for human consumption

5.Hard water causes scaling in water distribution systems

A1, 3, 4 & 5 only ✓ Correct

B1, 3 & 5 only

C2, 3, 4 & 5 only

D1, 2, 4 & 5 only

Correct answer: (A) 1, 3, 4 & 5 only

Explanation

Hardness occurs in surface and groundwater, arises from calcium and magnesium salts, is broadly safe to drink and causes scaling.

Statement 1 is right since both surface and underground waters can be hard.

Statement 2 is wrong because hardness lowers, not raises, the cleaning power of water with soap.

Statement 3 is right as carbonates of magnesium and calcium cause temporary hardness.

Statement 4 is right since hard water is generally safe, and Statement 5 is right as it causes scaling in pipes.

Boiling can remove temporary hardness by precipitating the carbonates.

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