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.

Hint:

The process of electrolysis of brine produces hydrogen, chlorine, and sodium hydroxide. The sodium hydroxide reacts with carbon dioxide to produce sodium carbonate, which is the precursor for washing soda.

Answer 1

(i) The acid and the base from which common salt (sodium chloride) is obtained are: Acid: Hydrochloric acid (HCl) Base: Sodium hydroxide (NaOH) The reaction between hydrochloric acid and sodium hydroxide gives sodium chloride (NaCl) and water as products: \[ {HCl} + {NaOH} \rightarrow {NaCl} + {H}_2{O} \] (ii) Sodium chloride (NaCl) is a neutral salt. This is because it is formed by the neutralization reaction between a strong acid (HCl) and a strong base (NaOH). Since both acid and base completely neutralize each other, the resultant salt is neutral in nature. 
(iii) (A) When electric current is passed through an aqueous solution of sodium chloride (brine), the process is called electrolysis of brine. The products obtained are: At the cathode, hydrogen gas (H\(_2\)) is produced. At the anode, chlorine gas (Cl\(_2\)) is produced. The reactions at each electrode are: \[ {At cathode: } 2{H}_2{O} + 2e^- \rightarrow {H}_2 + 2{OH}^- \] \[ {At anode: } 2{Cl}^- \rightarrow {Cl}_2 + 2e^- \]