RAJASTHAN PMT Rajasthan - PMT Solved Paper-2011

  • question_answer
    The \[{{t}_{1/2}}\] of a reaction is halved as the initial concentration of the reactant is doubled. What is the order of reaction?

    A)  First order         

    B)  Zero order

    C)  Second order    

    D)         Third order

    Correct Answer: C

    Solution :

    The half-life period of a reaction of nth order is related to initial concentration of reactant as                 \[{{t}_{1/2}}\propto \frac{1}{{{[{{A}_{0}}]}^{n-1}}}\] For two different half-life periods, their concentration are                 \[\frac{{{({{t}_{1/2}})}_{1}}}{{{({{t}_{1/2}})}_{2}}}=\frac{[{{A}_{0}}]_{2}^{n-1}}{{{[{{A}_{0}}]}^{n-1}}}={{\left\{ \frac{{{[{{A}_{0}}]}_{2}}}{{{[{{A}_{0}}]}_{1}}} \right\}}^{n-1}}\] or            \[\frac{1}{1/2}={{\left( \frac{2}{1} \right)}^{n-1}}\] or            \[2={{2}^{n-1}}\] or            \[n-1=1\] or            \[n=2\] \[\therefore \]Order of reaction\[=2\]


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