The half-life of iodine-131 is approximately 8 days. Find the amount of iodine-131 left from a 42 gram sample after 16 days.

Question

I'm studying for a final and I really don't get this. Help please :))

Answer 1

The start is with 42 grams of Iodine-131.

Its half life is approximately 8 days.

So after 8 days there are 42x1/2 = 21 grams.

Then after another 8 days or 16 days from the start, there is 21x1/2 = 10.5 grams.

y = (1/2)^d/8 where (1/2) is the half life factor, and d is the number of days of each half-life, and 8 is the half life period.