The half-life of cobalt-60 is 5.20 y. How many milligrams of a 2.000-mg sample remain after 6.55 years?

Question

Quizplus · Accepted Answer

The half-life of a substance is the time it takes for half of the substance to decay. After one half-life, half of the original amount remains; after two half-lives, half of that amount remains, or one-fourth of the original amount; and so on.In this problem, the half-life of cobalt-60 is 5.20 years. After 6.55 years, the number of half-lives that have passed is 6.55 years / 5.20 years = 1.26.After 1.26 half-lives, the fraction of the original amount that remains is (1/2)^1.26 = 0.418.Therefore, the amount of the original 2.000-mg sample that remains after 6.55 years is 2.000 mg * 0.418 = 0.835 mg.

The Half-Life of Cobalt-60 Is 5