Question

What do you understand about the hardness of water? Explain the permutit method for the removal of permanent hardness of water?

Answer 1

Hardness of water indicates that there is presence of soluble bicarbonates, chlorides and sulfates of calcium and magnesium. There are several ways to remove the hardness of water, they may be either permanent or temporary methods.

Complete answer:
Hardness of water is basically due to the presence of soluble bicarbonates, sulfates and chlorides of calcium and magnesium. Hard water consists of high mineral content. When the hard water is boiled, it leads to the deposition of the salts that’s why it is harmful for the boilers as it reduces its efficiency. Hard water is safe to drink but its long time usage may cause some problems like strains in skins, difficulty in using water appliances and clogging in pipes etc. This water is unsuitable for household or laundry purposes.
There are two types of hardness of water i.e. temporary and permanent hardness.
Temporary hardness of water due to the presence of magnesium and calcium carbonates. Temporary hardness of water can be removed easily by boiling the water. When the water boils, the soluble salts of $Mg{(HC{O_3})_2}$ are converted to insoluble salt $Mg{(OH)_2}$ which get easily separated from the water.
On the other hand, permanent hardness of water is due to the presence of chlorides and sulfides of magnesium and calcium in water. Here, the hardness of water cannot be removed from boiling water.
The permanent hardness of water can be removed by Gan’s permutit method. This method is also known as the zeolite method. In this method, permutit is used to remove the permanent hardness of water. Permutit is the sodium aluminum ortho silicate.
Reaction occurs in this method:
$N{a_2}A{l_2}S{i_2}{O_8}\,.\,x{H_2}O\,\, + \,\,C{a^ + }\, \to 2N{a^ + }\,\, + Ca\,A{l_2}S{i_2}{O_8}\,.\,x{H_2}O\,$

Note:
It is noted that a very common way to determine whether the water is hard or soft is that if the soap does not form lather in water then it is hard water, whereas if a soap forms lather in water then it indicates it’s a soft water. There are also other methods to remove the permanent hardness of water Calgon’s process and Ion exchange resin method.