JEE Main & Advanced Chemistry Chemical Kinetics / रासायनिक बलगतिकी Question Bank Critical Thinking Chemical Kinetics

  • question_answer
    The rate constant, the activation energy and the arrhenius parameter of a chemical reaction at \[{{25}^{o}}C\] are \[3.0\times {{10}^{-4}}{{s}^{-1}}\], \[104.4\,kJ\,mo{{l}^{-1}}\] and \[6.0\times {{10}^{14}}{{s}^{-1}}\] respectively. The value of the rate constant as \[T\to \infty \] is [IIT 1996]

    A)                 \[2.0\times {{10}^{18}}{{s}^{-1}}\]           

    B)                 \[6.0\times {{10}^{14}}{{s}^{-1}}\]

    C)                 Infinity 

    D)                 \[3.6\times {{10}^{30}}{{s}^{-1}}\] 

    Correct Answer: B

    Solution :

               \[{{T}_{2}}=T(say),\,T={{25}^{o}}C=298K,\,\,\]                    \[{{E}_{a}}=104.4\,\,\text{kJ}\,\,mo{{l}^{-1}}=104.4\times {{10}^{3}}\,\text{J}\,mo{{l}^{-1}}\]                    \[{{K}_{1}}=3\times {{10}^{-4}},\,\,{{K}_{2}}=\]?,                    \[\log \frac{{{K}_{2}}}{{{K}_{1}}}=\frac{{{E}_{a}}}{2.303R}\left[ \frac{1}{{{T}_{1}}}-\frac{1}{{{T}_{2}}} \right]\]                    \[\log \frac{{{K}_{2}}}{3\times {{10}^{-4}}}=\frac{104.4\times {{10}^{3}}\text{J}\,\,mo{{l}^{-1}}}{2.303\times (8.314\,\,\text{J}\,\,{{k}^{-1}}\,\,mo{{l}^{-1}})}\]                    \[\left[ \frac{1}{298K}-\frac{1}{T} \right]\,\,\text{As}\,\,\text{T}\to \infty \text{,}\frac{\text{1}}{\text{T}}\to 0\]                    \[\therefore \,\,\log \frac{{{K}_{2}}}{3\times {{10}^{-4}}}=\frac{104.4\times {{10}^{3}}\,\,\text{J}\,\,mo{{l}^{-1}}}{2.303\times 8.314\times 298}\]                    \[\log \frac{{{K}_{2}}}{3\times {{10}^{-4}}}=18.297,\,\,\frac{{{K}_{2}}}{3\times {{10}^{-4}}}\] \[=1.98\times {{10}^{18}}\] or                                 \[{{K}_{2}}=(1.98\times {{10}^{18}})\times (3\times {{10}^{-4}})=6\times {{10}^{14}}{{s}^{-1}}\]


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