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Question: Answered & Verified by Expert
$2 \mathrm{~g}$ of a radioactive sample having half-life of 15 days was synthesised on 1st Jan 2009. The amount of the sample left behind on 1st March, 2009 (including both the days) is
ChemistryChemical KineticsKCETKCET 2009
Options:
  • A $0 \mathrm{~g}$
  • B $0.125 \mathrm{~g}$
  • C $1 \mathrm{~g}$
  • D $0.5 \mathrm{~g}$
Solution:
2238 Upvotes Verified Answer
The correct answer is: $0.125 \mathrm{~g}$
$\begin{array}{llrl}\mathrm{N}=\mathrm{N}_{0}\left(\frac{1}{2}\right)^{\mathrm{n}} & & \\ \text { Given, } & \mathrm{N}_{0} =2 \mathrm{~g} \\ \mathrm{t}_{1 / 2} =15 \text { days } \\ \Rightarrow & \mathrm{T} =60 \text { days } \\ & \mathrm{n} =\frac{60}{15}=4 \\ & \mathrm{~N} =2\left(\frac{1}{2}\right)^{4} \\ \text { or } & \mathrm{N} =0.125 \mathrm{~g}\end{array}$

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