A radioactive isotope has a half-life of 50 years. its mass in 1980 was 800 grams. What will its mass be in the year 2020 ?
This is confusing me.... Does this solution assume that the ENTIRE mass is radioactive??? Then, I THINK there will be 459.48 gms of RADIOACTIVE material left, but the mass of the SAMPLE will be greater as some atoms that are no longer radioactive will remain...right?
Since the half-life=50 years, therefore,
40/50=.8 half-lives, then we have,
800 X 2^-.8=459.479...grams left after 40 years.