JEE Main & Advanced JEE Main Paper (Held on 08-4-2019 Morning)

  • question_answer
    For the reaction \[2A+B\to C,\]the values of initial rate at different reactant concentrations are given in the table below. The rate law for the reaction is :
    \[[A](mol\,{{L}^{-1}})\] \[[B](mol\,{{L}^{-1}})\] Initial Rate \[(mol\,{{L}^{-1}}{{s}^{-1}})\]
    0.05 0.05 0.045
    0.10 0.05 0.090
    0.20 0.10 0.72
    [JEE Main 8-4-2019 Morning]

    A) \[Rate=k\left[ A \right]\left[ B \right]\]

    B) \[Rate=k{{\left[ A \right]}^{2}}{{\left[ B \right]}^{2}}\]

    C) \[Rate=k\left[ A \right]{{\left[ B \right]}^{2}}\]

    D)   \[Rate=k{{\left[ A \right]}^{2}}\left[ B \right]\]

    Correct Answer: C

    Solution :

    \[r=K{{\left[ A \right]}^{x}}{{\left[ B \right]}^{y}}\] \[0.045=K{{\left( 0.05 \right)}^{x}}{{\left( 0.05 \right)}^{y}}\]                ....(a) \[0.090=K{{\left( 0.10 \right)}^{x}}{{\left( 0.05 \right)}^{y}}\]                ....(b) \[0.72=K{{\left( 0.20 \right)}^{x}}{{\left( 0.10 \right)}^{y}}\]                              ....(c) From (a)\[\div \](b), \[\frac{0.045}{0.090}={{\left( \frac{0.05}{0.10} \right)}^{x}}\Rightarrow x=1\] From (b)\[\div \](c), \[\frac{0.090}{0.720}={{\left( \frac{0.10}{0.20} \right)}^{x}}.{{\left( \frac{0.05}{0.10} \right)}^{y}}\Rightarrow y=2\] Hence, \[r=K\left[ A \right]\text{ }{{\left[ B \right]}^{2}}\] Correct option : (c)


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