Question

Which of the following statements regarding the property of hard water is/are correct?
1. Temporary hardness of water is due to the presence of soluble magnesium and calcium hydrogen carbonate.
2. Temporary hardness of water can be removed by boiling.
3. Calgon’s method is applied to remove the temporary hardness of the water.
4. Permanent hardness of water is removed by the dark's method.
Select the correct answer using the codes given below
A) $ 1 and 2 $
B) $ 1,2 and 3 $
C) $ 3 and 4 $
D) Only $ 2 $

Answer 1

Hint: Hardness of water is due to the salts present in it, the term hardness is used because with such a type of water it's hard to wash clothes. There are two types of hardness in water – temporary and permanent. A variety of methods are used to remove the hardness of the water.

Complete answer:
The magnesium and calcium salts like magnesium and calcium hydrogen carbonate give it temporary hardness, this hardness can be removed by boiling the water. At the point when we bubble water, the dissolved salts of $ Mg{\left( {HC{O_3}} \right)_2} $ is changed over to $ Mg{\left( {OH} \right)_2} $ which is insoluble and thus gets encouraged and is taken out. After filtration, the water we get is soft.
In the Calgon method, sodium-hexa-meta-phosphate (NaPO3)6 known as Calgon is used to remove the magnesium and calcium ions by absorbing them, hence this method can be used for the removal of hardness of water, although this method is used to remove the permanent hardness.
The use of the dark’s method is not significant for the removal of the hardness of the water.
Hence, the statements $ 1,2and3 $ are correct and option B is the correct answer.

Note:
The hardness of water can be removed by various methods like – boiling, Clark’s method, Gan’s Permutit Method, Calgon’s Process, Ion Exchange Resin Method, and treating the water with washing soda.