VMMC VMMC Medical Solved Paper-2005

  • question_answer
    Arrange \[\text{NH}_{\text{4}}^{\text{+}}\text{,}\,{{\text{H}}_{\text{2}}}\text{O,}\,{{\text{H}}_{\text{3}}}{{\text{O}}^{\text{+}}}\text{,}\,\text{HF}\] and \[\text{O}{{\text{H}}^{-}}\]in increasing order of acidic nature:

    A)  \[{{H}_{3}}{{O}^{+}}<NH_{4}^{+}<HF<O{{H}^{-}}<{{H}_{2}}O\]

    B)  \[NH_{4}^{+}<HF<{{H}_{3}}{{O}^{+}}<{{H}_{2}}O<O{{H}^{-}}\]

    C)  \[O{{H}^{-}}<{{H}_{2}}O<NH_{4}^{+}<HF<{{H}_{3}}{{O}^{+}}\]

    D)  \[{{H}_{3}}{{O}^{+}}>HF>{{H}_{2}}O>NH_{4}^{+}>O{{H}^{-}}\]

    Correct Answer: C

    Solution :

    Among the given species, correct order of increasing acidic strength is: \[O{{H}^{-}}<{{H}_{2}}O<NH_{4}^{+}<HF<{{H}_{3}}{{O}^{+}}\] \[\text{O}{{\text{H}}^{-}}\] is basic {i.e., it tends to gain a proton) and hence is least acidic. \[{{\text{H}}_{\text{2}}}\text{O}\] is neutral species. \[{{\text{H}}_{\text{3}}}{{\text{O}}^{\text{+}}}\] is most acidic as it readily loose proton.


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