JCECE Engineering JCECE Engineering Solved Paper-2008

  • question_answer
    The rate law for a reaction between the substances \[A\] and \[B\] is given by rate\[=k{{[A]}^{n}}{{[B]}^{n}}\]. On doubling the concentration of \[A\] and halving the concentration of \[B\], the ratio of the new rate to the earlier rate of the reaction will be as

    A) \[\frac{1}{{{2}^{m+n}}}\]                                             

    B) \[(m+n)\]

    C) \[(n-m)\]                            

    D) \[{{2}^{(n-m)}}\]

    Correct Answer: D

    Solution :

    Rate becomes \[{{x}^{y}}\] times if concentration is made \[x\] times of a reactant giving \[{{y}^{th}}\] order reaction.                 Rate\[=k{{[A]}^{n}}{{[B]}^{m}}\] Concentration of \[A\] is doubled, hence,\[x=2\],\[y=n\]and rate becomes\[={{2}^{n}}\]times Concentration of \[B\] is halved, hence \[x=\frac{1}{2}\] and \[y=m\] and rate becomes \[={{\left( \frac{1}{2} \right)}^{m}}\] times Net rate becomes \[={{(2)}^{n}}{{\left( \frac{1}{2} \right)}^{m}}\] times                                     \[={{(2)}^{n-m}}\]


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