How is the gas formed at the cathode in the chlor-alkali process tested?
Answer and explanation
Correct answer: By a pop sound near a burning splint
In the chlor-alkali process, concentrated brine is electrolysed. At the cathode, water is reduced and hydrogen gas is released: 2H₂O + 2e⁻ → H₂ + 2OH⁻. Hydrogen is combustible, so bringing a burning splint or flame close to the collected gas produces the characteristic ‘pop’ sound. Hence option B is correct. Lime water is a test for carbon dioxide, turmeric indicates a base under suitable conditions, and blue litmus turning red indicates acidity; none identifies hydrogen.
Frequently asked questions
What is the correct answer to this question?
By a pop sound near a burning splint
Why is this the correct answer?
In the chlor-alkali process, concentrated brine is electrolysed. At the cathode, water is reduced and hydrogen gas is released: 2H₂O + 2e⁻ → H₂ + 2OH⁻. Hydrogen is combustible, so bringing a burning splint or flame close to the collected gas produces the characteristic ‘pop’ sound. Hence option B is correct. Lime water is a test for carbon dioxide, turmeric indicates a base under suitable conditions, and blue litmus turning red indicates acidity; none identifies hydrogen.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
