F-21 has a half-life of 5 seconds. How long will it take a 50 g sample of F-21 to decay to a mass of 12.5 g?

Name: F-21 has a half-life of 5 seconds. How long will it take a 50 g sample of F-21 to decay to a mass of 12.5 g?
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Question

Quizplus · Accepted Answer

The number of half-lives needed for 50 g to decay to 12.5 g is 2.
50 → 25 → 12.5
Therefore, you just multiply 5 seconds by 2 to get 10s as the amount of time it took for this mass to decay.

F-21 Has a Half-Life of 5 Seconds