AIIMS AIIMS Solved Paper-2005

  • question_answer
    In the balanced chemical reaction, \[IO_{3}^{-}+a{{I}^{-}}+b{{H}^{+}}\xrightarrow{{}}c{{H}_{2}}O+d{{I}_{2}}\] a, b, c and d respectively corresponds to:

    A) 5, 6, 3, 3                               

    B) 5, 2, 6, 3               

    C)        3, 5, 3, 6               

    D)        5, 6, 5, 5

    Correct Answer: A

    Solution :

    \[\overset{+5}{\mathop{I}}\,O_{3}^{-}+{{I}^{-}}+{{H}^{+}}\xrightarrow{{}}{{H}_{2}}O+{{\overset{0}{\mathop{I}}\,}_{2}}\] (i) Oxidation half cell \[{{I}^{-}}\xrightarrow{{}}{{I}_{2}}\] Balancing the numbers of atoms \[2{{I}^{-}}\xrightarrow{{}}{{I}_{2}}\] Balancing charge \[2{{I}^{-}}\xrightarrow{{}}{{I}_{2}}+2{{e}^{-}}\]                         ?...(1) (ii) (a) Reduction half reaction \[IO_{3}^{-}+{{H}^{+}}\xrightarrow{{}}{{H}_{2}}O+{{I}_{2}}\] (1) Balancing number of atoms \[2IO_{3}^{-}+12{{H}^{+}}\xrightarrow{{}}6{{H}_{2}}O+{{I}_{2}}\] (2) Balancing the charge \[2IO_{3}^{-}+12{{H}^{+}}+10{{e}^{-}}\xrightarrow{{}}6{{H}_{2}}O+{{I}_{2}}\]     ...(2) Multiplying Eq. (1) by 5 and adding it to Eq. (2) \[\begin{matrix}    2{{I}^{-}}\xrightarrow{{}}{{I}_{2}}+2{{e}^{-}}\times 5  \\    2IO_{3}^{-}+12{{H}^{+}}+10{{e}^{-}}\xrightarrow{{}}6{{H}_{2}}O+{{I}_{2}}  \\    \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_  \\    2IO_{3}^{-}+10{{I}^{-}}+12{{H}^{+}}\xrightarrow{{}}6{{I}_{2}}+6{{H}_{2}}O  \\ \end{matrix}\] or    \[IO_{3}^{-}+5{{I}^{-}}+6{{H}^{+}}\xrightarrow{{}}3{{I}_{2}}+3{{H}_{2}}O\] Hence,  \[a=5,b=6,c=3,d=3\]


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