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

  • question_answer
    Hydrolysis of  DDT is a first order reaction, its half life is 10 years. Time to hydrolyse 10 g DDT to half is     [BVP 2004]

    A)                 100 years            

    B)                 50 years

    C)                 5 years 

    D)                 10 years

    Correct Answer: D

    Solution :

               \[K=\frac{0.693}{{{t}_{1/2}}}=\frac{0.693}{10\,\text{years}}\]                    If initial concentration \[a=10\ gm\]and final concentration \[x=\frac{a}{2}=5\ gm\]                    then, \[t=\frac{2.303}{K}\log \frac{a}{a-x}\] \[=\frac{2.303}{.693}\times 10\times \log \frac{10}{5}\]                                 \[=\frac{2.303\times 10\times \log 2}{.693}\]\[=\frac{2.303\times 10\times 0.301}{0.693}=10\ \text{years}\].


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