What is the half-life of Iron-60 that decays from 70 g to 8.75 g in 9 days?

Answer 1

A simple formula to use for these types of problem is FR = 0.5ⁿ

FR = fraction remaining

n = number of half lives that have elapsed

In this problem the fraction remaining is 8.75 g/70 g = 0.125

We can now find n, the number of half lives that have elapsed.

0.125 = 0.5ⁿ

log 0.125 = log 0.5 n

-0.903 = -0.301

n = 3 half lives have elapsed

Since it took 9 days for 3 half lives, that means the half life is 3 days