NEET Sample Paper NEET Sample Test Paper-58

  • question_answer
    The time taken for 90% of a first order reaction to complete is approximately:

    A) 1.1 times that of half-life

    B) 2.2 times that of half-life

    C) 3.3 times that of half-life

    D) 4.4 times that of half-life

    Correct Answer: C

    Solution :

    [c] 3.3 times that of half-life \[{{t}_{90%}}=\frac{2.303}{k}\,\log \frac{a}{a-0.9a}\] \[=\frac{2.303}{k}\log \,10\] \[=\frac{2.303}{k}\] \[{{t}_{{}^{1}/{}_{2}}}=\frac{2.303}{k}\log \frac{a}{a-{}^{a}/{}_{2}}\] \[{{t}_{{}^{1}/{}_{2}}}=\frac{2.303}{k}\log \frac{2a}{a}\] \[=\frac{2.303\times 0.3010}{k}\] \[\therefore \,\,\frac{{{t}_{90%}}}{{{t}_{{}^{1}/{}_{2}}}}=\frac{1}{0.3010}=3.3\Rightarrow {{t}_{90%}}={{t}_{{}^{1}/{}_{2}}}\times 3.3\]


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