NEET Chemistry NEET PYQ-Halogen Family

  • question_answer
    \[HgC{{l}_{2}}\]and \[{{l}_{2}}\] both when dissolved in water containing \[{{l}^{-}}\]ions the pair of species formed is [NEET-2017]

    A) \[H{{g}_{2}}{{l}_{2}},{{l}^{-}}\]

    B) \[Hg{{l}_{2}},l_{3}^{-}\]

    C) \[Hg{{l}_{2}},{{l}^{-}}\]

    D) \[Hgl_{4}^{2-},l_{3}^{-}\]

    Correct Answer: D

    Solution :

    [d] In a solution containing \[HgC{{l}_{2}},{{l}_{2}}\]and \[{{l}^{-}},\]  both \[HgC{{l}_{\,}}_{2}\]and \[{{l}_{2}}\]compete for\[{{l}^{-}}.\]
    Since formation constant of \[{{[Hg{{l}_{4}}]}^{2-}}\] \[1.9\times {{10}^{30}}\] which is very large as compared with \[{{l}_{3}}^{-}({{K}_{f}}=700)\]
    \[\therefore \]\[{{l}^{-}}\]will preferentially combine with \[HgC{{l}_{2}}.\]
    \[HgC{{l}_{2}}+2{{l}^{-}}\to \underset{\text{Red}\,\text{ppt}}{\mathop{Hg{{l}_{2}}\downarrow +2C{{l}^{-}}}}\,\]
    \[Hg{{l}_{2}}+2{{l}^{-}}\to \underset{So\operatorname{lub}le}{\mathop{{{[Hg{{l}_{4}}]}^{2-}}}}\,\]


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