Hardness of Water:Causes, Types and Treatments

Q.

Clarks method of water softening uses-

Q.

The hardness of a water sample containing ${10}^{-3}\mathrm{M}{\mathrm{MgSO}}_4$ expressed as ${\mathrm{CaCO}}_3$ equivalents (in ppm)is (molar mass of ${\mathrm{MgSO}}_4$is $120.37$$\mathrm{g}/\mathrm{mol}$)

Q.

Permanent hardness is caused due to:

1. Magnesium Bicarbonate

2. All of the above

3. Magnesium carbonate

4. Magnesium sulphate

Q.

Write the formula of cryolite. Give its function in the extraction of aluminium.

Q.

Polyphosphates are used as a water softening agents because they

1. Form soluble complexes with anionic species

2. Precipitate anionic species

3. Form soluble complexes with cationic species

4. Precipitate cationic species

Q.

What are hydrated salts? Give three examples.

Q.

What is the cause of hardness of water? Name the salts used for hardness of water.

Q.

Which one of the following process will produce hard water?

1. Saturation of water with ${\mathrm{CaSO}}_4$

2. Addition of ${\mathrm{Na}}_2{\mathrm{SO}}_4$ to water

3. Saturation of water with ${\mathrm{CaCO}}_3$

4. Saturation of water with ${\mathrm{MgCO}}_3$

Q.

Which ions will cause hardness in water?

Q.

Explain the permutit method for softening hard water.

Q.

Differentiate between the following.

Soft water and hard water

Q. 1000g of a water sample contained a calcium salt equivalent to 1g of CaCO3. The hardness of that water sample is ? option 1)100ppm option 2) 500 ppm option 3)1000ppm option 4)20, 000 ppm

Q.

Water is said to be soft when

1. It easily forms lather with soap

2. When it contains lots of salts and impurities.

3. when it feels soft.

4. It doesn't form lather with soap

Q. What is the permanent hardness of water? How can it be removed? [2 Marks]

Q. Soap is not effective in hard water.

1. True
2. False

Q.

209(g). Give one example of copper(II) salt through its chemical and molecular formula.

Q.

How is temporary hardness of water removed ?

Q.

What are the causes of temporary hardness of water.

Q.

What are the causes for

(a) Temporary hardness

(b) Permanent hardness

Q. A student purchases common salt from the market which is contaminated with ammonium chloride. Identify the technique that he should adopt to obtain pure NaCl.

1. Sublimation
2. Sedimentation
3. Distillation
4. Crystallisation

Q.

Temporary hardness of water is caused by:

1. calcium and magnesium chloride

2. calcium and magnesium bicarbonate

3. calcium and magnesium sulphate

4. all of these

Q.

Name the substances in each case which causes:

(i) Temporary hardness in water

(ii) Permanent hardness in water

Q. Temporary hardness of water can be removed by Clark's Method using:

1. $N{a}_{2}C{O}_3$
2. $NaCl$
3. $NaOH$
4. $Ca(OH{)}_2$

Q. The temporary hardness of water can be removed by Clark's Method using _____. [1mark]
A. $NaCl$
B. $NaOH$
C. $N{a}_{2}C{O}_3$
D. $Ca(OH{)}_2$

Q. From recorded data:
Weight of U-tube______$20.36$g
Weight of U-tube and calcium chloride before______$39.32$g
Weight of U-tube and calcium chloride after_______$57.32$g
Weight of boat and contents(copper oxide)before_____$30.23$g
Weight of boat and contents after_____$14.23$g
Weight of boat_____$5.00$g
What is the reaction for the first $CaC{l}_2$ drying tube?

1. Generate water
2. Absorb hydrogen
3. Absorb water that evaporates from the flask
4. Decompose the water from the flask
5. Act as a catalyst for the combination of hydrogen and oxygen

Q. Soft water does not produce much lather.

1. False
2. True

Q. 3.55g of bleaching powder when treated with acetic acid and excess of Kl liberated iodine which
required 60mL of 0.5N sodium thiosulphate solution. The percentage of available chlorine in the
sample is

Q.

How the permanent hardness is removed?

Q. The ionic product of water at 60degree C is 9.61*10^-14.The pH of water at 60degree C is

Q.

Temporary hardness of water is due to the presence of

1. Magnesium bicarbonate

2. Calcium chloride

3. Magnesium sulphate

4. Calcium carbonate