Q1. [2]
(B) The industrial process used for the manufacture of caustic soda involves electrolysis of an aqueous solution of compound 'X'. In this process, two gases 'Y' and 'Z' are liberated. 'Y' is liberated at cathode and 'Z', which is liberated at anode, on treatment with dry slaked lime forms a compound 'B'. Name X, Y, Z and B.
Previously asked in CBSE board exam
2023 31/4/1 Q21 (B)
Generated by claude-sonnet-4-6 · 2026-06-15 06:44 · grounding rag
Model Answer
- X = Sodium chloride (NaCl) / brine (aqueous solution)
- Y = Hydrogen (H₂) — liberated at cathode
- Z = Chlorine (Cl₂) — liberated at anode
- B = Bleaching powder — formed when Cl₂ reacts with dry slaked lime Ca(OH)₂
$$2\text{NaCl}(aq) + 2\text{H}_2\text{O}(l) \xrightarrow{\text{electrolysis}} 2\text{NaOH} + \text{H}_2\uparrow + \text{Cl}_2\uparrow$$
Explanation
This question tests the chlor-alkali process. Remember the key facts: electrolysis of brine (NaCl solution) gives NaOH (caustic soda) as the main product, H₂ at cathode, and Cl₂ at anode. Cl₂ + dry slaked lime [Ca(OH)₂] → bleaching powder. Examiners expect all four names correctly identified. Writing the equation adds value even in a 2-mark answer.
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