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.

1. Name the acid and the base from which common salt can be obtained.    (1)
2. State the nature (acidic/basic/neutral) of sodium chloride. Give a reason for the justification for your answer.    (1)
3. 1. 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.    (2)
      OR
   2. How is washing soda obtained from sodium chloride? Give the chemical equation of the reactions involved in the process.    (2)

Answer 1

(i) Acid is Hydrochloric and the base is sodium hydroxide.

(ii) As strong acids and bases can fully ionize salt and water without the need for additional H⁺/OH⁻ ions, sodium chloride is naturally neutral.

(iii) (A) When electric current is passed through aqueous NaCl, the electrolyte would contain. H⁺, OH⁻, Na⁺ and Cl⁻ ions, where H⁺ and Na⁺ will move towards the cathode and OH⁻ and Cl⁻ at the anode. Depending on the reactivity of H₂ gas, bubbles would be seen at the cathode and greenish-yellowish chlorine gas at the anode.

OR

(B) Brine reacts with carbon dioxide and ammonia gas, then is heated to produce washing soda from NaCl.

\[\ce{NaCl + NH3 + H2O + CO2 -> NaHCO3 + NH4Cl}\]

\[\ce{2NaHCO3 ->[\Delta] Na2CO3 + CO2 + H2O}\]

\[\ce{NO2CO3 + 10H2O -> \underset{Washing soda}{Na2CO3*10H2O}}\]