DUMET Medical DUMET Medical Solved Paper-2001

  • question_answer
    A first order reaction is 75% complete after 32 min. When was 50% of the reaction completed?

    A)  16 min        

    B)  8 min

    C)  4 min          

    D)  32 min

    Correct Answer: A

    Solution :

    Key Idea: \[t=\frac{2.303}{k}\log \frac{a}{a-x}\] Given t = 32 min a = 100 (initial amount) \[(a-x)=25\] (mass left after time 0 \[32=\frac{2.303}{k}\log \frac{100}{25}\] \[32k=2.303\log 4\] \[\therefore \] \[k=0.0432\] Now for 50% of the reaction \[k=0.0432,\,a=100,\,a-x=50\] \[t=\frac{2.303}{K}\log \frac{a}{a-x}\] \[=\frac{2.303}{0.0432}\log \frac{100}{50}\] \[=53.310\log 2\] \[=53.310\times 0.3010\] = 16 min


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