BCECE Medical BCECE Medical Solved Papers-2004

  • question_answer
    Arrange the following as increase in oxidation number:
    (i) \[M{{n}^{2+}}\]
    (ii) \[Mn{{O}_{2}}\]
    (iii) \[KMn{{O}_{4}}\]
    (iv) \[{{K}_{2}}Mn{{O}_{4}}\]

    A)  (i) > (ii) > (iii) > (iv)

    B)  (i) < (ii) < (iv) < (iii)

    C)  (ii) < (iii) < (i)  < (iv)

    D)  (iii) > (i)   > (iv) > (ii)

    Correct Answer: B

    Solution :

    Key Idea: The sum of oxidation states of all elements in a compound is always zero. (i) Oxidation state of Mn in \[M{{n}^{2+}}=+2\] (ii) Let oxidation state of Mn in \[Mn{{O}_{2}}=x\] \[\therefore \] \[x+(2x-2)=0\] \[\therefore \] \[x=+4\] (iii) Let oxidation state of Mn in \[KMn{{O}_{4}}=x\] \[\therefore \] \[+1+x+(-2\times 4)=0\] \[\therefore \] \[x=+7\] (iv) Let oxidation state of Mn in \[{{K}_{2}}Mn{{O}_{4}}=x\] \[\therefore \] \[(+1\times 2)+x+(-2\times 4)=0\] \[\therefore \] \[x=+6\] \[\therefore \] Increasing order of oxidation states is (i) < (ii) < (iv) < (iii)


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