BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    The colour of iodine solution is discharged by shaking it with aqueous solution of:

    A) sodium sulphite

    B) sulphuric acid

    C) sodium sulphate

    D) sodium thiosulphite

    Correct Answer: D

    Solution :

    Key Idea: The colour of reagent disappears when the products formed during reaction are colourless. \[\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,sodium \\  thiosulphite \end{smallmatrix}}{\mathop{2N{{a}_{2}}{{S}_{2}}{{O}_{3}}}}\,+\underset{\begin{smallmatrix}  iodine \\  (purple\,coloured) \end{smallmatrix}}{\mathop{{{I}_{2}}}}\,\xrightarrow{{}}\] \[\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,sodium \\  thiosulphite \end{smallmatrix}}{\mathop{2N{{a}_{2}}{{S}_{2}}{{O}_{3}}}}\,+\underset{\begin{smallmatrix}  iodine \\  (purple\,coloured) \end{smallmatrix}}{\mathop{{{I}_{2}}}}\,\xrightarrow{{}}\]


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