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Question: Answered & Verified by Expert
A first order reaction is $50 \%$ completed in $1.26 \times 10^{14} \mathrm{~s}$. How much time would it takes for 100\% completion?
ChemistryChemical KineticsJIPMERJIPMER 2017
Options:
  • A $1.26 \times 10^{15} \mathrm{~s}$
  • B $2.52 \times 10^{14} \mathrm{~s}$
  • C $2.52 \times 10^{28} \mathrm{~s}$
  • D Infinite
Solution:
2292 Upvotes Verified Answer
The correct answer is: Infinite
$k$-for first order. $\frac{0.693}{t_{1 / 2}}=\frac{0.693}{1.26 \times 10^{14}}$ for $100 \%$ completion.
$\because t=\frac{2.303}{k} \log \frac{a}{a-x}$
$t=\frac{2.303 \times 1.26 \times 10^{14}}{0.693} \log \frac{100}{0}$
$\therefore t=\infty$

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