BCECE Engineering BCECE Engineering Solved Paper-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 \[Mn{{O}_{2}}=x\] \[\therefore \]  \[x+(2x+2)=0\] \[\therefore \]  \[x=+\,4\] (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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