A radioactive isotope has a half-life of . If the initial mass of the isotope was , the mass of it r — Nuclear Chemistry and Radioactivity Chemistry Question
Question
A radioactive isotope has a half-life of $3\text{ hours}$. If the initial mass of the isotope was $256\text{ g}$, the mass of it remaining undecayed after $18\text{ hours}$ will be:
Answer: A
💡 Solution & Explanation
Total time = 18 hrs, Half-life = 3 hrs. Number of half-lives ($n$) = $18/3 = 6$. Amount remaining $N_t = N_0(1/2)^n = 256 \times (1/2)^6 = 256 / 64 = 4.0\text{ g}$.
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