Bleaching Action Of Chlorine
Chlorine acts as a bleaching agent for cotton and paper; on what chemical principle does its bleaching action depend in the presence of moisture?
Select the correct option:
Solution
Oxidation of the coloured matter by nascent oxygen
The bleaching action of chlorine is an oxidative process that requires moisture. In the presence of water, chlorine reacts to form hypochlorous acid, Cl_2 + H_2O → HCl + HOCl, and the hypochlorous acid decomposes to release nascent oxygen, HOCl → HCl + [O]. This highly reactive nascent oxygen oxidises the coloured organic substances in cotton, paper, or dyes, converting them into colourless products and thereby bleaching the material. Because the action is oxidation, chlorine bleaching is permanent rather than temporary. The option of reduction of the dye is incorrect, since the process is oxidative. The option of simple physical adsorption describes the action of charcoal, not chlorine. The option of neutralisation of acids is unrelated to bleaching. The oxidative bleaching mechanism of chlorine through nascent oxygen is a standard NCERT Group 17 fact. Plausibility check: bleaching fails in the complete absence of moisture, confirming that the reaction with water to give oxidising nascent oxygen is essential.
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About This Question
- Subject
- chemistry
- Chapter
- p-block elements
- Topic
- bleaching action of chlorine
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Oxidation of the coloured matter by nascent oxygen
The bleaching action of chlorine is an oxidative process that requires moisture. In the presence of water, chlorine reacts to form hypochlorous acid, Cl_2 + H_2O → HCl + HOCl, and the hypochlorous acid decomposes to release nascent oxygen, HOCl → HCl + [O]. This highly reactive nascent oxygen oxidises the coloured organic substances in cotton, paper, or dyes, converting them into colourless products and thereby bleaching the material. Because the action is oxidation, chlorine bleaching is permanent rather than temporary. The option of reduction of the dye is incorrect, since the process is oxidative. The option of simple physical adsorption describes the action of charcoal, not chlorine. The option of neutralisation of acids is unrelated to bleaching. The oxidative bleaching mechanism of chlorine through nascent oxygen is a standard NCERT Group 17 fact. Plausibility check: bleaching fails in the complete absence of moisture, confirming that the reaction with water to give oxidising nascent oxygen is essential.
This easy difficulty chemistry question is from the chapter p-block elements, covering the topic of bleaching action of chlorine. It appeared in the 2025 exam.
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