CBSE Class 10 Sample Paper Science Solution - For 2023 Boards

Question 28 - Identify the gasses evolved - teachoo.jpg


(a) Identify the gasses evolved at the anode and cathode in the above experimental set up.

(b) Name the process that occurs. Why is it called so?

(c) Illustrate the reaction of the process with the help of a chemical equation.



(a) Brine is a solution of salt (NaCl) in water.

  • When subjected to electrolysis , it separates into its constituent ions , Na+ and Cl-.
  • The positive ion is attracted to the cathode (-ve) and Negative is attracted to the anode (+ve).
  • H+ ions are also produced and attracted to the cathode .
  • Hence, Cl- ions and H+ ions combine to form Cl 2 and H 2 at the anode and cathode respectively and are liberated as gases .

Anode : Chlorine

Cathode : Hydrogen 

(b) Chlor alkali process .

The industrial production of Sodium Hydroxide and chlorine by the process of electrolysis of Sodium Chloride Solution is known as the Chlor Alkali Process.

 The products obtained are alkali , chlorine gas and hydrogen gas.

(c) 2NaCl(aq) + 2H 2 O(l) 2NaOH(aq) + Cl 2 (g) + H 2 (g) 

Chor-Alkali process reaction - Teachoo.jpg

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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo