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

  • question_answer
    A first order reaction with respect to the reactant A has a rate constant of \[6\ {{\sec }^{-1}}\]. If we start with [A] = 0.5 mol/litre, then in what time the concentration of A becomes 0.05 mol/litre [DCE 2004]

    A)                 0.384 sec             

    B)                 0.214 sec

    C)                 3.84 sec

    D)                 0.402 sec

    Correct Answer: A

    Solution :

               For the first order reaction \[t=\frac{2.303}{K}\log \frac{a}{a-x}\]                    Given: \[a=0.5\ mol/litre\]; \[a-x=0.05\ ,mol/litre\]                    \[K=6{{\sec }^{-1}}.\]                 \[t=\frac{2.303}{6}\log \frac{0.5}{0.05}=\frac{2.303}{6}\log 10\]\[=\frac{2.303}{6}=0.384\sec \].


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