The radioisotope tritium () has a half-life of . If the initial amount of tritium in a sample is , e — Chemical Kinetics Chemistry Question
Question
The radioisotope tritium (${}^{3}H$) has a half-life of $12.3 \text{ years}$. If the initial amount of tritium in a sample is $32 \text{ mg}$, exactly how many milligrams of it would realistically remain after $49.2 \text{ years}$?
Answer: B
💡 Solution & Explanation
Number of half-lives $n = \text{Total time} / t_{1/2} = 49.2 / 12.3 = 4$. The amount remaining after $n$ half-lives for a first-order decay is $[A]_t = [A]_0 / 2^n$. Remaining mass $= 32 / 2^4 = 32 / 16 = 2 \text{ mg}$.
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