BCECE Medical BCECE Medical Solved Papers-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. \[\underset{\begin{smallmatrix}  sodium \\  thiosulphite \end{smallmatrix}}{\mathop{2N{{a}_{2}}{{S}_{2}}{{O}_{3}}}}\,\,\,+\underset{\begin{smallmatrix}  iodine \\  (purple\text{ }coloured) \end{smallmatrix}}{\mathop{{{I}_{2}}}}\,\,\,\xrightarrow{{}}\]                      \[\underset{\begin{smallmatrix}  sodium\text{ }tetrathionate \\  (colourless) \end{smallmatrix}}{\mathop{N{{a}_{2}}{{S}_{4}}{{O}_{6}}}}\,\,\,\,\,\,+2Nal\]


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