A 6.0 g sample of Ra-223 decays to 0.75 g.If the half-life of Ra-223 is 11.7 days,how much time has elapsed?

Name: A 6.0 g sample of Ra-223 decays to 0.75 g.If the half-life of Ra-223 is 11.7 days,how much time has elapsed?
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Quizplus · Accepted Answer

The sample decays from 6.0 g to 0.75 g, which means it goes through 3 half-lives (6.0 to 3.0, 3.0 to 1.5, and 1.5 to 0.75 g). Since the half-life of Ra-223 is 11.7 days, the total time elapsed is 3 half-lives x 11.7 days/half-life = 35.1 days.

A 60 G Sample of Ra-223 Decays to 0