JEE Main & Advanced Sample Paper JEE Main Sample Paper-10

  • question_answer
    For a complex reaction \[P\xrightarrow{k}\]Products \[{{E}_{{{a}_{1}}}}=200KJ/mol,\]\[{{E}_{{{a}_{2}}}}=90KJ/mol,\]\[{{E}_{{{a}_{3}}}}=80KJ/mol,\] Overall rate constant k is related to individual rate constant by the equation\[k={{\left( \frac{{{k}_{1}}{{k}_{2}}}{{{k}_{3}}} \right)}^{2/3}}\] Activation energy (kJ/mol) for the overall reaction is

    A)  140 kJ/mol                        

    B)  240 kJ/mol

    C)  370 kJ/mol                        

    D)  30 kJ/mol

    Correct Answer: A

    Solution :

     Idea Problem includes concept of Arrhenius equation for different rate ?constant of a common reaction. To solve this problem student is advised to write the Arrhenius equation for every rate constant. Then, put the value in\[k=\left( \frac{{{k}_{1}}{{k}_{2}}}{{{k}_{3}}} \right)2/3\]to get the value of\[{{E}_{a}}\] Putting\[k=A{{e}^{-{{E}_{a}}IRT}}\] \[{{k}_{1}}=A{{e}^{\frac{-{{E}_{a1}}}{RT}}},{{k}_{2}}=A{{e}^{-\frac{{{E}_{{{a}_{2}}}}}{RT}}}\] \[{{K}_{3}}=A{{e}^{-\frac{{{E}_{{{a}_{3}}}}}{RT}}}\] \[k={{\left( \frac{A{{e}^{-\frac{{{E}_{{{a}_{1}}}}}{RT}}}\cdot A{{e}^{-\frac{{{E}_{a}}_{_{2}}}{RT}}}}{A{{e}^{-{{E}_{{{a}_{3}}}}/RT}}} \right)}^{2/3}}=A{{e}^{-{{E}_{a}}/RT}}\] \[{{E}_{a}}=\frac{2}{3}[{{E}_{{{a}_{1}}}}+{{E}_{{{a}_{2}}}}-{{E}_{{{a}_{3}}}}]\] \[{{E}_{a}}=\frac{2}{3}[200+90-80]=\frac{2}{3}[210]\] = 140 kJ/mol TEST Edge Students are advised to study the concept of Arrhenius equation at different temperatures. Since, these types of questions are also asked.


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