# Chemistry

Given a 800 mg sample of Thorium-231 decomposes via beta emission with a half life of 25.5 hours, how long would it take, in days, for the sample to decay down to 25 mg?

231 0 231
Th -> Beta + Pa
90 -1 91

800 mg/ 25 mg

1. 25/800 = 1/32 = 1/2^5
so, it will take 5 half-lives

posted by Steve

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