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Radioactive waste is difficult to dispose of due to the long time periods needed

ID: 887463 • Letter: R

Question

Radioactive waste is difficult to dispose of due to the long time periods needed before the radiation effectively disappears. The US protocol is to store the waste for 10 half-lives of the material after which the waste is no longer considered radioactive. After this time, very little of the original chemical remains. Assume you conducted an experiment with 1.00 g of bismuth-207 that has a half-life of 32.2 years. How much radioactive bismuth-207 will remain when your waste is considered not radioactive? Report the answer in milligrams.

Explanation / Answer

For this problem we can use the formula, to calculate the amount of substance left after n half lives = A0 / 2 n

The US protocol is to store the waste for 10 half-lives of the material after which the waste is no longer considered radioactive, hence n = 10, and [A0] = 1 g

Amount of the substance left after 10 half lives = A0 / 2 10 = 1/ 1024 = 0.0009765 g = 0.9765 mg