NEET Chemistry NEET PYQ-Chemical Kinetics

  • question_answer
    The rate of first order reaction is \[1.5\times {{10}^{-2}}\,mo{{l}^{-1}}\,{{\min }^{-1}}\] at 0.5 M concentration of the reactant. The half-life of the reaction is: [AIPMT (S) 2004]

    A) 0.383 mm

    B) 23.1 mm

    C) 8.73 mm

    D) 7.53 mm

    Correct Answer: B

    Solution :

    [b] For the first order reaction
    Rate\[\left( \frac{dx}{dt} \right)=k[A]\]
    \[[A]\to \]concentration of reactant
    \[k\to \]rate constant
    Given that
    \[\frac{dx}{dt}=1.5\times {{10}^{-2}}\,mol\,\,{{L}^{-1}}\]
                \[k=?\]and\[[A]=0.5\,M\]
    \[\therefore \]      \[1.5\times {{10}^{-2}}=k\times 0.5\]
    \[\therefore \]      \[k=\frac{1.5\times {{10}^{-2}}}{0.5}=3\times {{10}^{-2}}{{\min }^{-1}}\]
    For first order reaction
    Half-life period \[{{t}_{1/2}}=\frac{0.693}{k}=\frac{0.693}{3\times {{10}^{-2}}}\]
                            \[=23.1\,\,\min \]


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