Hard Water and Soft Water

Q. Which among the following is/are the reasons why hard water is not used in industrial boilers?

1. It causes corrosion of the boiler.
2. The heating efficiency decreases.
3. They produce rich lather with soap.
4. It contains small amount of salts.

Q.

Hard water gives lather with soap easily.

1. True

2. False

Q.

What is the cause of the hardness of water?

Q. Choose the correct option regarding the following assertion and reason.

Assertion: Use of hard water in industrial boilers reduces heating efficiency.
Reason: Hard water produces scales on the inner walls of the boilers.

1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2. Both Assertion and Reason are true and Reason is not the correct explanation of Assertion.
3. Only Assertion is true.
4. Both Assertion and Reason are false

Q.

A water is said to be hard if:

1. It does not contain minerals.

2. It does not lather readily with soap.

3. It contains minerals.

4. It lathers readily with soap.

Q.

Hard water cannot be used for washing clothes.

1. True
2. False

Q.

The temporary hardness of water is due to the presence of:

1. Magnesium bicarbonate

2. Magnesium sulphate

3. Calcium carbonate

4. Calcium chloride

Q. Why erasers become hard after some months or years?

Q.

There are two tubs full of water, A and B.
The water in tub A contains ${\text{MgCl}}_2$ salts in very low concentration. Tub B on the other hand contains ${\text{MgCl}}_2$ salts in high concentration. Clothes are washed using water from these tubs separately. The clothes washed using water from which of the two tubs will be cleaner?

1. A

2. Both will be equally clean

3. B

4. Neither would clean the clothes

Q.

Which of the following is/are true?

1. Soaps are more effective in hard water than detergents

2. Detergents are more effective in hard water than soaps.

3. Both are equally effective

4. Detergents work only in soft water.

Q.

There are two water samples one in test-tube A and another in test-tube B. It was observed that water in both test-tubes A and B does not give lather with soap. However, after boiling the water in both the test-tubes A and B, the water in test-tube B does give lather with soap. Which among the following statements is correct?

1. Water in both the test-tubes is permanent hard water.

2. Water in test-tube A is permanent hard water while in test-tube B is temporary hard water.

3. Water in test-tube A is temporary hard water while in test-tube B is permanent hard water.

4. Water in both the test-tubes is temporary hard water.

Q.

The hardness of water can be detected using ______.

1. electrolysis

2. lathering soap

3. litmus paper

4. thermometer

Q. Soft water does not produce much lather.

1. False
2. True

Q.

Soap forms insoluble precipitates with calcium and magnesium ions present in hard water.

1. True

2. False