10. With reference to Hard water, which of the statements given is/are correct?
1. Hardness in water is caused by soluble salts of calcium and magnesium.
2. Hard water is known to reduce the efficiency of boilers.
10. With reference to Hard water, which of the statements given is/are correct?
1. Hardness in water is caused by soluble salts of calcium and magnesium.
2. Hard water is known to reduce the efficiency of boilers.
The correct option is C c. Both 1 and 2
Answer-c
Presence of calcium and magnesium salts in the form of hydrogen carbonate, chloride and sulphate in
water makes water hard‘. Hard water does not give lather with soap. Hard water forms cum/precipitate with soap. Soap containing sodium stearate C17H35COONa.reacts with hard water to precipitate out Ca/Mg stearate. It is, therefore, unsuitable for laundry.
It is harmful for boilers as well, because of deposition of salts in the form of scale. This reduces the
efficiency of the boiler. The hardness of water is of two types:
i. temporary hardness, and
ii. permanent hardness.
Temporary hardness is due to the presence of magnesium and calcium hydrogen carbonates
Permanent hardness is due to the presence of soluble salts of magnesium and calcium in the form of
chlorides and sulphates in water.
c. Both 1 and 2
Answer-c
Presence of calcium and magnesium salts in the form of hydrogen carbonate, chloride and sulphate in
water makes water hard‘. Hard water does not give lather with soap. Hard water forms cum/precipitate with soap. Soap containing sodium stearate C17H35COONa.reacts with hard water to precipitate out Ca/Mg stearate. It is, therefore, unsuitable for laundry.
It is harmful for boilers as well, because of deposition of salts in the form of scale. This reduces the
efficiency of the boiler. The hardness of water is of two types:
i. temporary hardness, and
ii. permanent hardness.
Temporary hardness is due to the presence of magnesium and calcium hydrogen carbonates
Permanent hardness is due to the presence of soluble salts of magnesium and calcium in the form of
chlorides and sulphates in water.
