Name: Dihydrogen as a Fuel
Uploaded: 2019-07-19
Duration: 7 min 24 s
Description: A good fuel should release a huge amount of energy on combustion. Let’s explore one such fuel that has promising potential for use as a non-polluting fuel of...

Question

Explain the terms hard water and soft water. Write a note on
I. Ion exchange method and
II. Calgon method for the removal of hardness of water.

Accepted Answer

The presence of calcium and magnesium salts in the form of hydrogen carbonate, chloride and sulphate in water makes water ‘hard’. Hard water does not give lather with soap. Water free from soluble salts of calcium and magnesium is called soft water. It gives lather with soap easily.

There are certain ways in which the hardness of water can be removed these are:

I. Ion-exchange method: This method is also called zeolite/permutit process. Hydrated sodium aluminium silicate is zeolite/permutit. For the sake of simplicity, sodium aluminium silicate ( ${NaAlSiO}_{4}$ ) can be written as $NaZ$ . When this is added in hard water, exchange reactions take place.

$2 NaZ (s) + M^{2 +} (aq) \to {MZ}_{2} (s) + 2 {Na}^{+} (aq) (M = Mg, Ca)$

Permutit/zeolite is said to be exhausted when all the sodium in it is used up. It is regenerated for further use by treating with an aqueous sodium chloride solution.

${MZ}_{2} (s) + 2 NaCl (aq) \to 2 NaZ (s) + {MCl}_{2} (aq)$

II. Calgon’s method: Sodium hexametaphosphate ( ${Na}_{6} P_{6} O_{18}$ ), commercially called ‘calgon’, when added to hard water, the following reactions take place.

${Na}_{6} P_{6} O_{18} \to 2 {Na}^{+} + {Na}_{4} P_{6} O_{18}^{2 -} (M = Mg, Ca) M^{2 +} + {Na}_{4} P_{6} O_{18}^{2 -} \to {[{Na}_{2} {MP}_{6} O_{18}]}^{2 -} + 2 {Na}^{+}$

The complex anion keeps the ${Mg}^{2 +}$ and ${Ca}^{2 +}$ ions in solution and hence the hardness of water is removed.

Explain the terms hard water and soft water. Write a note on
I. Ion exchange method and
II. Calgon method for the removal of hardness of water.

Important Questions on Hydrogen and its Compounds

Learn and Prepare for any exam you want !

Explain the terms hard water and soft water. Write a note on I. Ion exchange method and II. Calgon method for the removal of hardness of water.

Important Questions on Hydrogen and its Compounds

Learn and Prepare for any exam you want !

Explain the terms hard water and soft water. Write a note on
I. Ion exchange method and
II. Calgon method for the removal of hardness of water.