DUMET Medical DUMET Medical Solved Paper-2001

  • question_answer
    At \[{{90}^{o}}C\] pure water has\[{{H}_{3}}{{O}^{+}}={{10}^{-6}}mol/{{L}^{-1}}\]. The value of \[{{K}_{w}}\] at \[{{90}^{o}}C\] is:

    A)  \[{{10}^{-6}}\]          

    B)  \[{{10}^{-12}}\]

    C)  \[{{10}^{-14}}\]         

    D)  \[{{10}^{-8}}\]

    Correct Answer: B

    Solution :

    Key Idea: \[{{K}_{w}}=[{{H}^{+}}]\,[O{{H}^{-}}]\] \[{{H}_{2}}O[{{H}^{+}}]+[O{{H}^{-}}]\] \[\therefore \] \[[{{H}^{+}}]=[O{{H}^{-}}]\,([{{H}^{+}}])=[{{H}_{3}}{{O}^{+}}]\] \[\therefore \] \[{{K}_{w}}={{[{{H}_{3}}{{O}^{+}}]}^{2}}\] Given, \[[{{H}_{3}}{{O}^{+}}]={{10}^{-6}}mol/L\] \[\therefore \] \[{{K}_{w}}={{({{10}^{-6}})}^{2}}\] \[={{10}^{-12}}\]


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