Water Hardness and Treatment

Q.

What are the methods of removing hardness of water?

Q.

Which of the following is not true?

1. The hardness of water depends on its behaviour towards soap.

2. The temporary hardness is due to the presence of calcium and magnesium bicarbonates.

3. Permanent hardness is due to the presence of soluble calcium and magnesium sulphates, chlorides and nitrates.

4. Permanent hardness can be removed by boiling the water.

Q.

A water sample contains magnesium bicarbonates. It does not lather with soap. How can we make the water sample useful for cleaning clothes?

1. Boiling

2. Cooling

3. By addition of sodium

4. By addition of water

Q.

What is hard water examples?

Q. Which of these are pure substances and which are mixtures?

Q.

Temporary hardness can be removed by

1. Boiling

2. Cooling

3. Adding $\mathrm{Calcium}\mathrm{carbonate}$

4. Adding $\mathrm{Magnesium}\mathrm{carbonate}$

Q. A $10$% solution of $NaCl$ means that in $100g$ of solution there is:

1. $58.5g$ $NaCl$
2. $10g$ $NaCl$
3. $5.85g$ $NaCl$
4. $94g$ $NaCl$

Q.

Give two disadvantages of hard water.

Q.

1. Which of the following chemical substances can be used for removing permanent hardness of water by precipitation reaction?

1. baking soda

2. washing soda

3. alum

4. quick lime

Q.

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

1. True

2. False

Q. ___ is an example of hard water.

1. Sea water
2. Spring water
3. Lake water
4. Rain water

Q.

Temporary and permanent hardness of water can be removed by:-

1. For temporary hardness:- ${\text{Na}}_2{\text{CO}}_3$

   For permanent hardness:- ${\text{Ca(OH)}}_2$

2. For temporary hardness:- ${\text{Ca(OH)}}_2$

   For permanent hardness:- Boiling

3. For temporary hardness:- Boiling

   For permanent hardness:- ${\text{Ca(OH)}}_2$

4. For temporary hardness:- Boiling

   For permanent hardness:- ${\text{Na}}_2{\text{CO}}_3$

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 both the test-tubes is temporary hard water

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

Q.

Hard water gives lather with soap easily.

1. True

2. False

Q. Assertion (A): Hard water gives easy lather with soap.
Reason (R): Salts of calcium and magnesium react with soap to form insoluble salts.

1. (A) and (R) both are correct and (R) is the correct explanation of (A).
2. (A) and (R) both are correct but (R) is not the correct explanation of (A).
3. (A) is correct but (R) is not correct.
4. (A) is not correct but (R) is correct.

Q.

Permanent hardness of water can be removed by:

1. Boiling

2. Addition of washing soda

3. Addition of potassium permanganate

4. Addition of slaked lime

Q. The hardness of water is due to the presence of:

1. calcium and magnesium salts
2. sodium and magnesium salts
3. calcium and sodium salts
4. ammonium and sodium salts