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JEE Main & Advanced Chemistry Chemical Kinetics / रासायनिक बलगतिकी Question Bank Rate law and Rate Constant

  • question_answer
    A reaction that is of the first order with respect to reactant A has a rate constant \[6{{\min }^{-1}}.\] If we start with \[[A]=0.5\,mol\,\,{{l}^{-1}}\], when would \[[A]\]reach the value 0.05mol \[{{l}^{-1}}\]  [KCET 2000]

    A)                 0.384 min            

    B)                 0.15 min

    C)                 3 min    

    D)                 3.84 min

    Correct Answer: A

    Solution :

               We know that for first order kinetics                     \[k=\frac{2.303}{t}\log \frac{a}{a-x}\]                    \[(a-x)=0.05\,\,mol\,\,{{l}^{-1}}\],\[6=\frac{2.303}{t}\log \frac{0.5}{0.05}\]                                 or \[t=\frac{2.303}{6}\log \frac{0.5}{0.05}=\frac{2.303}{6}=0.384\,\min \]


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