What is the calgon process in chemistry?

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Hint: We know that water is very important for the survival of life. Water contains many minerals in it and hence, it can be classified into soft water and hard water. Hard water is the water which contains mainly bicarbonates, carbonates and sulphate salts of calcium and magnesium. This hard water is not suitable for human consumption, so it has to be converted into soft water and the process used for this conversion is known as the calgon process.

Complete answer:
We know that water consists of many minerals and based on the amount of these minerals in it, it can be classified as soft water and hard water. Hard water is the water which contains mainly bicarbonates, carbonates and sulphate salts of calcium and magnesium. This hard water is not suitable for human consumption, so it has to be converted into soft water.
Calgon process is used to remove the permanent hardness of water. Calgon is the name of a complex salt known as sodium hexametaphosphate. Chemical formula of calgon is

(N a P O_{3})_{6} .

On adding calgon to the hard water, magnesium and calcium ions are replaced by sodium ions and hence, permanent hardness of water is removed. The chemical reactions taking place in this process are given as:

2 C a C l_{2} + N a_{2} [N a_{4} (P O_{3})_{6}] \to N a_{2} [C a_{2} (P O_{3})_{6}] + 4 N a C l

2 M g S O_{4} + N a_{2} [N a_{4} (P O_{3})_{6}] \to N a_{2} [M g_{2} (P O_{3})_{6}] + 2 N a_{2} S O_{4}

Note:
We should remember some properties of hard water and soft water. Hard water has some characteristic taste while soft water has a salty taste. When we use hard water with soap, it forms a film rather than foam while in case of soft water, a good amount of foam is formed. We can also remove the hardness of water by the ion exchange method.