Question

Common salt is a very important chemical compound for our daily life. It's chemical name is sodium chloride and it is used as a raw material in the manufacture of caustic soda, washing soda, baking soda etc. It is also used in the preservation of pickles, butter, meat etc.

(i) Name the acid and the base from which common salt can be obtained.

(ii) State the nature (acidic/basic/neutral) of sodium chloride. Give reason for the justification for your answer.

(iii) (A) What happens when electric current is passed through an aqueous solution of sodium chloride (called brine)? Name the products obtained along with the corresponding places in the electrolytic cell where each of these products is obtained.

OR

(iii) (B) How is washing soda obtained from sodium chloride? Give chemical equation of the reactions involved in the process.

Answer 1

(i) Hydrochloric acid and sodium hydroxide (base).

(ii) Sodium chloride is neutral in nature as it is formed by the neutralisation reaction of a strong acid with a strong base.

(iii) (A) When electricity is passed through an aqueous solution of sodium chloride it undergoes electrolytic decomposition.

Hydrogen gas is obtained at cathode

Chlorine gas is obtained at anode

Sodium hydroxide solution is formed near the cathode.

OR

(iii) (B) Washing soda is obtained from sodium chloride by the reaction of brine with carbon dioxide and ammonia gas followed by heating.

\(NaCl+H_2O+CO_2+NH_3\longrightarrow NH_4Cl+NaHCO_3\)

\(2NaHCO_3\overset {Heat}{\longrightarrow}Na_2CO_3+H_2O+CO_2\)

\(Na_2CO_3+10H_2O \longrightarrow {Na_2CO_3} . {10H_2O}\)