JEE Main & Advanced Sample Paper JEE Main Sample Paper-45

  • question_answer
    For the reaction,\[{{[Cu{{\left( N{{H}_{3}} \right)}_{4}}]}^{2+}}+{{H}_{2}}O\xrightarrow{\,}\,{{[Cu{{(N{{H}_{3}})}_{3}}{{H}_{2}}O]}^{2+}}\]\[+N{{H}_{3}}\]the   net   rate   is \[\frac{dx}{dt}=2.0\times {{10}^{-4}}{{s}^{-1}}\]\[\,{{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}-3.0\times {{10}^{5}}\,L\,mo{{l}^{-1}}\,{{s}^{-1}}\]            \[{{[Cu{{(N{{H}_{3}})}_{3}}{{H}_{2}}O]}^{2+}}\,[N{{H}_{3}}]\] Then the ratio of rate constants of the forward and backward reactions is

    A)  \[0.66\times {{10}^{-9}}\,mol\,{{L}^{-1}}\]      

    B)  \[105\times {{10}^{-5}}\,mo{{l}^{-1}}\,L\]

    C)  \[2.0\times {{10}^{-4}}\,{{s}^{-1}}\]                 

    D)  \[3.0\times {{10}^{5}}\,mo{{l}^{-1}}\,{{s}^{-1}}\]

    Correct Answer: A

    Solution :

     \[\frac{dx}{dt}={{K}_{f}}\,{{[Cu\,{{(N{{H}_{3}})}_{4}}]}^{2+}}\] \[-{{K}_{b}}{{[Cu{{(N{{H}_{3}})}_{3}}{{H}_{2}}O]}^{2+}}\,[N{{H}_{3}}]\] \[\frac{{{K}_{f}}}{{{K}_{b}}}=\frac{2.0\times {{10}^{-4}}{{s}^{-1}}}{3.0\times {{10}^{5}}\,\text{L}\,\text{mo}{{\text{l}}^{-1}}\,{{\text{s}}^{-1}}}\] \[=0.66\times {{10}^{-9}}mol\,{{L}^{-1}}\]


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