BCECE Medical BCECE Medical Solved Papers-2003

  • question_answer
    In which of the following reactions, hydrogen is acting as an oxidising agent?

    A)  With \[Li\] to form \[LiH\]

    B)  With \[{{I}_{2}}\] to give HI

    C)  With S to give \[{{H}_{2}}S\]

    D)  None of the above

    Correct Answer: A

    Solution :

    Key Idea: Oxidising agent is one which undergoes reduction. Decreasing in oxidation number shows reduction. Find oxidation number in all given reactions to decide in which of them hydrogen is oxidising agent. [a]          \[Li={{\overset{0}{\mathop{H}}\,}_{2}}\xrightarrow{{}}\overset{+1}{\mathop{2Li}}\,\,\overset{-1}{\mathop{H}}\,\] Oxidation number of hydrogen is decreasing from 0 to -1. So \[{{H}_{2}}\] is acting as oxidising agent in this reaction. [b]          \[{{\overset{0}{\mathop{H}}\,}_{2}}+{{I}_{2}}\xrightarrow{{}}\overset{+1}{\mathop{2HI}}\,\] \[\because \] Oxidation number of hydrogen is increasing. Hz is not acting as oxidising agent in this reaction. [c]           \[\overset{0}{\mathop{{{H}_{2}}}}\,+S\xrightarrow{{}}\overset{+1}{\mathop{{{H}_{2}}}}\,S\] \[\because \] Oxidation number of hydrogen is increasing \[\therefore \] \[{{H}_{2}}\] is not acting as oxidising agent in this reaction. \[\therefore \] [a] is correct answer.


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