Question

The method used to remove temporary hardness of water is?
A.Calgon’s method
B.Clark’s method
C.Ion-exchange method
D.Synthetic resins method

Answer 1

Hint:You should know that it is also known as lime softening. It is also effective at removing a variety of microorganisms and dissolved organic matter by flocculation.

Complete step by step answer:
-As we all know hard water can cause scaling problems in water heaters and soap does not lather well in hard water. Therefore, some water utilities soften water to improve its quality for domestic use. Lime softening is best suited to groundwater sources, which have relatively stable water quality.
-Now let us understand about hard water and soft water.
-In general hard water is one which doesn't leather with soap. Whereas soft water easily forms leather with water it is due to presence of certain salts in water. Generally two type of hardness exist, temporary hardness and permanent hardness. Water that contains bicarbonate of calcium and magnesium or of both is called temporary hard water and water that contains chlorides or sulphates of calcium or magnesium or of both is called Permanent water.
-Clark's method is a process for the large-scale removal of temporary hardness from water. This process involves the addition of a controlled quantity of slaked lime (calcium hydroxide)
$Ca{ (HC{ O }_{ 3 }) }_{ 2 }+Ca{ (OH) }_{ 2 }\longrightarrow CaC{ O }_{ 3 }+2{ H }_{ 2 }O$
$Mg{ (HC{ O }_{ 3 }) }_{ 2 }+Ca{ (OH) }_{ 2 }\longrightarrow CaC{ O }_{ 3 }+MgC{ O }_{ 3 }+2{ H }_{ 2 }O$
-Therefore, the method used to remove temporary hardness of water is Clark’s method. Hence, option B is the required answer.

Note:
You should know that hard water when used for drinking for long period can lead to stomach disorders. Especially as we know hard water contains magnesium sulphate can weaken the stomach permanently.