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JEE Main & Advanced Sample Paper JEE Main Sample Paper-12

  • question_answer
    A substance 'A' decomposes in solution following first order kinetics. Flask I contains 1 L of a 1M solution of A and flask II contains 100 ml of a 0.6 M solution. After 8 hours the concentration of A in flask I has become 0.25. What will be the time taken for concentration of A in flask II to become 0.3M?

    A)  0.4                                        

    B)  2.4 h

    C)  4.0 h

    D)  Can't be calculated since rate constant is not given

    Correct Answer: C

    Solution :

     The concentration of A remains 1/4th in 8 hours. Therefore \[\frac{1}{{{2}^{n}}}=\frac{1}{4}n=2\]and \[{{E}_{{\scriptstyle{}^{1}/{}_{2}}}}\]is \[8=n\times {{t}_{{\scriptstyle{}^{1}/{}_{2}}}};{{t}_{{\scriptstyle{}^{1}/{}_{2}}}}=4;\] In 4 hours 0.6 will become 0.3


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