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Chemistry

What percent of a sample of a radioactive element whose halflife equals 5.0 years will decay after 25?

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May 31, 2009 9:59PM

if you have 100g of a radioactive material with a half life of 5.0 years then, 5.0 years after the material was created there will be 50g of radioactive material left, another 5 years and it will be 25g, then another 5 years 12.5 radioactive material will be left, another 5 years, 6.25g, then 3.125g will be left after another 5 years, that is 25 years so what percent of 100 is 3.125? your answer is 3.125% of the material will be left