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NEET Chemistry Chemical Kinetics / रासायनिक बलगतिकी Question Bank Self Evaluation Test - Chemical Kinetics

  • question_answer
    A reaction takes place in various steps. The rate constant for first, second, third and fifth steps are \[{{k}_{1}},{{k}_{2}},{{k}_{3}}\] and \[{{k}_{4}}\] respectively The overall rate constant is given by \[k=\frac{{{k}_{2}}}{{{k}_{3}}}{{\left( \frac{{{k}_{1}}}{{{k}_{5}}} \right)}^{1/2}}\]. If activation energy are 40,60,50 and 10 kJ/mol respectively, the overall energy of activation (kJ/ mol) is: 

    A) 10  

    B) 20

    C) 25                                

    D) none of these

    Correct Answer: C

    Solution :

    [c] \[k=A.{{e}^{-{{E}_{a}}/}}^{(RT)}\] \[\therefore \]   Effective overall energy of activation \[{{E}_{a}}={{E}_{a}}(2)-{{E}_{a}}(3)+\frac{1}{2}{{E}_{a}}(1)-\frac{1}{2}{{E}_{a}}(5)\] \[=60-50+\frac{1}{2}\times 40-\frac{1}{2}\times 10=25\,kJ/mol\]


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