The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass.

Question

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 125 grams of a radioactive isotope, how much will be left after 3 half-lives? round your answer to the nearest gram. 

Answer 1

T = half-life

 

m(t) = m₀ (0.5)^t/T

 

m(3T) = (125 g) (0.5)^3T/T = (125 g) (0.5)³ = 15.625 g ≅ 16 g