RAJASTHAN ­ PET Rajasthan PET Solved Paper-2008

  • question_answer
    Which of the following is correct for the reaction? \[MnO_{4}^{-}+CO_{4}^{2-}+{{H}^{+}}\xrightarrow[{}]{{}}M{{n}^{2+}}+C{{O}_{2}}+{{H}_{2}}O\]

    A)   \[M{{n}^{2+}}\] - 5          \[C{{r}_{2}}O_{4}^{2-}\]-2       \[C{{O}_{2}}\]- 4         \[{{H}^{+}}\]-10

    B)   \[M{{n}^{2+}}\] -2         \[C{{r}_{2}}O_{4}^{2-}\]- 5       \[C{{O}_{2}}\]-10       \[{{H}^{+}}\]-16

    C)   \[M{{n}^{2+}}\] -6         \[C{{r}_{2}}O_{4}^{2-}\]-8       \[C{{O}_{2}}\]- 16       \[{{H}^{+}}\]-18

    D)   \[M{{n}^{2+}}\] - 10       \[C{{r}_{2}}O_{4}^{2-}\]- 12     \[C{{O}_{2}}\]-24       \[{{H}^{+}}\]-12

    Correct Answer: B

    Solution :

     \[MnO_{4}^{-}+{{C}_{2}}O_{4}^{2-}+{{H}^{+}}\xrightarrow[{}]{{}}M{{n}^{2+}}+C{{O}_{2}}+{{H}_{2}}O\] \[{{C}_{2}}O_{4}^{2-}\xrightarrow[{}]{{}}2C{{O}_{2}}+2{{e}^{-}}\] (oxidation) ...(i) \[MnO_{4}^{-}+8{{H}^{+}}+5{{e}^{-}}\xrightarrow[{}]{{}}M{{n}^{2+}}+4{{H}_{2}}O\] (reduction) ...(ii) Equation (i) is multiplied by 5 and equation (ii) is multiplied by 2 and then on adding \[5{{C}_{2}}O_{4}^{2-}\xrightarrow[{}]{{}}10C{{O}_{2}}+10{{e}^{-}}\] \[\begin{align}   & \underline{2MnO_{4}^{-}+16{{H}^{+}}+10{{e}^{-}}\xrightarrow[{}]{{}}2M{{n}^{2+}}+8{{H}_{2}}O} \\  & 2MnO_{4}^{-}+5{{C}_{2}}O_{4}^{2-}+16{{H}^{+}}\xrightarrow[{}]{{}} \\ \end{align}\] \[2M{{n}^{2+}}+10C{{O}_{2}}+8{{H}_{2}}O\]


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