J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    For the first order reaction half-life is 14 s, the time required for the initial concentration to reduce to 1/8 of its value is

    A) \[{{(14)}^{3}}s\]        

    B)  28 s

    C)  42 s          

    D) \[{{(14)}^{2}}s\]

    Correct Answer: C

    Solution :

     \[N={{N}_{0}}\times {{\left( \frac{1}{2} \right)}^{n}}\] \[\frac{1}{8}{{N}_{0}}={{N}_{0}}\times {{\left( \frac{1}{2} \right)}^{n}}\] \[n=3\] \[T=n\times {{t}_{1/2}}\] \[=3\times 14=42\,S\]


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