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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 26

  • question_answer
    In the volumetric estimation of Fe (II) with \[C{{r}_{2}}O_{7}^{2-}\]in acidic medium,\[{{K}_{3}}[Fe{{(CN)}_{6}}]\] is used as an external indicator. The end point will be reached when the solution of iron salt

    A) starts giving blue colour with indicator

    B) ceases to give blue colour with indicator

    C)  starts giving red colour with indicator

    D)  ceases to give red colour with indicator.

    Correct Answer: B

    Solution :

    [b]: Fe(II) gives blue colour with \[{{K}_{3}}[Fe{{(CN)}_{6}}]\]but Fe(III) does not. \[3F{{e}^{2+}}+2{{K}_{3}}[Fe{{(CN)}_{6}}]\to \underset{Blue}{\mathop{F{{e}_{3}}[Fe}}\,{{(CN)}_{6}}]+6{{K}^{+}}\]


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