The decay of a radioactive isotope follows first-order kinetics. Iodine-131, used to treat cancer of the thyroid gland, has a half-life of days. If g of iodine-131 is present in a sample initially, what mass of iodine-131 is present exactly hours later

Complete Question:

Iodine-131 is a radioactive isotope with a half-life of 8 days. How many grams of a 64 g sample of iodine-131 will remain at the end of 24 days? (It's an example of a likely question. In the question given, the time is given in hours, which must be converted by days, 1 day = 24 hours).

Answer:

8 g.

Explanation:

The half-life is the time needed to the mass decay by half, thus, if the initial mass is M and the final mass is m:

m = M/2ⁿ

Where n is how much half-lives had passed, thus

n = time / (half-life time)

n = 24/8

n = 3

m = 64/2³

m = 64/8

m = 8 g