Phosphorus-32 has a half-life of 14 days. What fraction of a sample of this isotope will remain after 6 weeks?

Name: Phosphorus-32 has a half-life of 14 days. What fraction of a sample of this isotope will remain after 6 weeks?
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Question

Quizplus · Accepted Answer

After 6 weeks (which is 42 days), 3 half-lives of phosphorus-32 have passed (since 42 days / 14 days per half-life = 3 half-lives). After each half-life, the amount of the substance is halved. Therefore, after 3 half-lives, the fraction remaining is (1/2)^3 = 1/8.

Phosphorus-32 Has a Half-Life of 14 Days