If the half-life of an isotope is 5 hr, the amount of 20.0 g remaining after 15 hr will be ________.

Name: If the half-life of an isotope is 5 hr, the amount of 20.0 g remaining after 15 hr will be ________.
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After 15 hours, which is three half-lives (15 hr / 5 hr/half-life = 3 half-lives), the amount of the isotope remaining would be $20.0 \, \text{g} \times (\frac{1}{2})^3 = 20.0 \, \text{g} \times \frac{1}{8} = 2.5 \, \text{g}$.

If the Half-Life of an Isotope Is 5 Hr, the Amount