Question

What is meant by demineralised water?
A. Water free from cation and anion.
B. Water free from minerals dissolved in it.
C. Water free from impurities.
D. Water free from ${\text{N}}{{\text{a}}^{\text{ + }}}$ and ${{\text{K}}^{\text{ + }}}$ ions.

Answer 1

Water has some dissolved ions, impurities etc. The demineralised water is processed water. The name demineralised water, itself indicates its purity.

Complete answer:
Water has dissolved minerals ions and different-different kinds of impurities. The demineralised water, as the name indicates does not have minerals and salts.
The water completely free from minerals and salts dissolved in it is known as demineralised water.
The demineralised water is free from impurities and cation and anion such as ${\text{N}}{{\text{a}}^{\text{ + }}}$ and ${{\text{K}}^{\text{ + }}}$ ions. But the option (A), (C) and (D) are not correct because the water only free from cation and anion or the water only free from ${\text{N}}{{\text{a}}^{\text{ + }}}$ and ${{\text{K}}^{\text{ + }}}$ ions or the water only free from impurity is not the demineralised water.

Therefore, option (B) Water free from minerals dissolved in it, is correct.

Additional Information: The demineralised water is obtained by one of the following methods:
- Deionization
- Distillation
- Membrane filtration
- Ion exchange method
Demineralised water is different from distilled water. Distilled water is obtained by boiling the water and then re-condensing.
Demineralised water is harmful to drink because it does not has minerals such ${\text{N}}{{\text{a}}^{\text{ + }}}$ and ${{\text{K}}^{\text{ + }}}$ ions which are necessary for proper body functioning.

Note: Demineralised water is also known as deionized water. The demineralised water is free from all minerals and any impurity including the ions of sodium, potassium, calcium, magnesium, chlorides, sulphates and nitrates etc.