The half-life of bromine-74 is 25 min.How much of a 4.0 mg sample is still active after 75 min?

Name: The half-life of bromine-74 is 25 min.How much of a 4.0 mg sample is still active after 75 min?
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Quizplus · Accepted Answer

After 75 minutes, which is three half-lives of bromine-74 (25 min x 3 = 75 min), the amount of active sample would have halved three times. Starting with 4.0 mg, after one half-life it would be 2.0 mg, after two half-lives 1.0 mg, and after three half-lives 0.5 mg.

The Half-Life of Bromine-74 Is 25 Min