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Question: Answered & Verified by Expert
After 2 hours the amount of a certain radioactive substance reduces to $1 / 16^{\text {th }}$ of the original amount (the decay process follows first-order kinetics). The half-life of the radioactive substance is
ChemistryChemical KineticsKVPYKVPY 2011 (SA)
Options:
  • A $15 \mathrm{~min}$
  • B $30 \mathrm{~min}$
  • C $45 \mathrm{~min}$
  • D $60 \mathrm{~min}$
Solution:
1142 Upvotes Verified Answer
The correct answer is: $30 \mathrm{~min}$
$\frac{0.693}{t_{1 / 2}}=\frac{2.303}{2 \times 60} \log \frac{a}{a / 16}$
$t_{1 / 2}=30 \mathrm{~min}$

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