JEE Main & Advanced Chemistry The p-block Elements-II Question Bank Halogen Family

  • question_answer In which of the following pairs does the first gas bleaches flowers by reduction while the second gas does so by oxidation [Manipal MEE 1995]

    A) \[CO\] and \[C{{l}_{2}}\]

    B) \[S{{O}_{2}}\] and \[C{{l}_{2}}\]

    C) \[{{H}_{2}}\] and \[B{{r}_{2}}\]

    D) \[N{{H}_{3}}\] and \[S{{O}_{2}}\]

    Correct Answer: B

    Solution :

    \[S{{O}_{2}}\] bleaches flower by reduction \[2{{H}_{2}}O+S{{O}_{2}}\,\to \,{{H}_{2}}S{{O}_{4}}+2[H]\] \[2[H]+\underset{\text{flower}}{\mathop{\text{Coloured}}}\,\text{  }\xrightarrow{\text{Reduction}}\,\underset{\text{reduced  flower}}{\mathop{\text{Colourless}}}\,\] This bleaching is temporary because reduced flower again oxidised by air to form coloured flower \[C{{l}_{2}}+{{H}_{2}}O\,\to \,2HCl+[O]\] \[[O]+\underset{\text{flower}}{\mathop{\text{Coloured}}}\,\xrightarrow{\text{Oxidation}}\,\underset{\text{Oxidised flower}}{\mathop{\text{Colourless}}}\,\text{ }\] This bleaching is permanent because oxidised flower remains colourless.


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