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1 INORGANIC CHEMISTRY MCQS

What is the most commonly used bleaching agent?

  • Alcohol
  • Carbon dioxide
  • Chlorine
  • Sodium chloride
Correct Answer: C. Chlorine

Detailed Explanation

Bleaching agents are substances used to remove color from materials such as fabrics, paper, and wood pulp. Among all bleaching agents, chlorine (Cl₂) is the most widely used because of its strong oxidizing properties and effectiveness in breaking down colored compounds.


Chlorine acts as a bleaching agent mainly by oxidation. When chlorine gas is dissolved in water, it forms hypochlorous acid (HClO):


Cl2+H2O⇌HCl+HClOCl₂ + H₂O ⇌ HCl + HClOCl2+H2OHCl+HClO


Hypochlorous acid is an unstable compound that readily releases nascent oxygen (O)(O)(O). This nascent oxygen oxidizes the colored substances (chromophores) present in natural dyes and organic materials, converting them into colorless compounds.


For example, the oxidation of organic dyes can be represented as:


Dye+[O]→Colorless compound\text{Dye} + [O] → \text{Colorless compound}Dye+[O]Colorless compound


Because of this strong bleaching action, chlorine is extensively used in industries. Its major applications include:




  • Paper and pulp industry: for whitening paper.




  • Textile industry: for bleaching cotton and linen.




  • Water treatment: chlorine is used to disinfect and kill microorganisms by oxidation.




  • Household cleaning products: sodium hypochlorite (NaOCl), which is produced from chlorine, is the active ingredient in liquid bleach.




Comparing with other options:




  • Alcohol is not a bleaching agent; it is mainly used as a solvent and disinfectant.




  • Carbon dioxide is an inert gas, not capable of bleaching.




  • Sodium chloride (NaCl) is common salt and does not have bleaching properties.




Thus, among the given options, chlorine is the most common bleaching agent due to its strong oxidizing action and wide industrial use.

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