Question

Sodium carbonate or washing soda or soda ash is:
(A) Sodium salt of sulphuric acid.
(B) Sodium salt of carbonic acid
(C) Ammonium salt of carbonic acid
(D) Potassium salt of carbonic acid.

Answer 1

Hint: We know that sodium carbonate as the name suggests is made up of sodium, carbon and oxygen. Sodium carbonate is white in colour and it has a very strong alkaline taste. We should know from which acid it is produced by a chemical reaction.

Complete step by step solution: We know that the common names of sodium carbonate are washing soda or soda ash. Sodium carbonate is an alkaline salt. It has a very strong alkaline taste. The solution of sodium carbonate turns the red litmus paper into blue. This shows that sodium carbonate is alkaline in nature. The pH of sodium carbonate is 10.52.
Sodium carbonate is prepared from carbonic acid which is a weak acid and sodium hydroxide which is a strong base.
The molecular formula for carbonic acid is ${{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$ and the molecular formula for sodium hydroxide is ${\text{NaOH}}$.
The reaction of carbonic acid with sodium hydroxide is as follows:
\[{{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}} + {\text{NaOH}} \to {\text{N}}{{\text{a}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}} + 2{{\text{H}}_{\text{2}}}{\text{O}}\]
The product formed is sodium carbonate. The molecular formula for sodium carbonate is \[{\text{N}}{{\text{a}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}\].
From the chemical formula of sodium carbonate we can say that sodium carbonate is a sodium salt of carbonic acid.
Thus, sodium carbonate or washing soda or soda ash is sodium salt of carbonic acid.

Thus, the correct option is (B) sodium salt of carbonic acid.

Note: Sodium carbonate is widely used in the manufacturing of soaps and detergents, manufacturing of glass and manufacturing of rayon which is a polymer. Sodium carbonate is used as a water softening agent. It is also used as a food additive as an anticaking agent, stabiliser, etc. it is used in toothpastes as a foaming agent.