Gold-198 has a half-life of approximately 3 days. If a 100 g sample of gold-198 decays for 9 days, approximately how much gold-198 remains in the sample?

Question

Quizplus · Accepted Answer

After 9 days, which is three half-lives of gold-198 (3 days per half-life), the amount remaining would be $100g \times (\frac{1}{2})^3 = 100g \times \frac{1}{8} = 12.5g$, which rounds to approximately 13g.

Gold-198 Has a Half-Life of Approximately 3 Days