Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2007

  • question_answer
    The time of completion of \[90%\] of a first order reaction 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 :

    Half-life period of first order reaction is \[{{t}_{1/2}}=\frac{2.303\times 0.3010}{k}\]         ??(i) Time for completion of 90% of a first order reaction is                 \[{{t}_{90}}=\frac{2.303}{k}\log \frac{100}{10}\] \[\therefore \]  \[{{t}_{90}}=\frac{2.303}{k}\]                      .,,,(ii) On dividing Eq. (i) by (ii), we get                 \[\frac{{{t}_{1/2}}}{{{t}_{90}}}=\frac{2.303\times 0.3010}{k}\times \frac{k}{2.303}\] \[\Rightarrow \]               \[\frac{{{t}_{1/2}}}{{{t}_{90}}}=\frac{0.3010}{1}\] \[\Rightarrow \]               \[{{t}_{90}}=\frac{1}{0.3010}\times {{t}_{1/2}}\] \[\therefore \]  \[{{t}_{90}}=3.322\times {{t}_{1/2}}\]


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