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 3 half-lives (9 days / 3 days per half-life), the amount of gold-198 would have halved 3 times. Starting with 100 g, after one half-life (3 days), it would be 50 g; after two half-lives (6 days), it would be 25 g; and after three half-lives (9 days), it would be approximately 12.5 g, which rounds to 13 g.

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