Question

What is the formula of Calgon?
a.) \[{\left( {NaP{O_3}} \right)_6}\]
b.) \[M{g_3}{\left( {P{O_4}} \right)_2}\]
c.) \[N{a_3}P{O_4}\]
d.) \[MgS{O_4}\]

Answer 1

Hint: Try to recall that calgon is used to remove the permanent hardness of water and its trade name is sodium hexametaphosphate. Now, by using this you can easily find the correct option from the given ones.

Complete step by step solution:
It is known to you that hardness of water is of two types:
Temporary hardness: This type of hardness can be easily removed by simply boiling the hard water. The hardness is due to the presence of bicarbonates of calcium and magnesium.
Permanent hardness: Permanent hardness of water is due to the presence of soluble chlorides and sulphates of calcium and magnesium. This type of hardness cannot be removed simply by boiling the water.
So, to remove the permanent hardness of water, the Calgon process is used. This method is the most modern method of the softening of water.
In this method, harmful calcium and magnesium ions present in hard water are sequestered in the form of soluble complexes by adding some substances.
The commonly used calgon for this purpose is sodium hexametaphosphate, \[N{a_6}{P_6}{O_{18}}\] or \[{\left( {NaP{O_3}} \right)_6}\].
Calgon combines with calcium and magnesium ions to form complex ions which are soluble in water.
Therefore, from above we can say that option A is the correct option to the given question.

Note: It should be remembered to you that the calgon is also used in synthetic detergents to check the wastage of soap during washing of clothes and also for removing boiler scales.
Also, you should remember that the water softened by the calgon process can be used for laundry and household washing purposes.