Question

The half-life of iodine-131 is 8.07 days. If 1.3 g are left after 93.2 days, how many grams werein the original sample?

Answer 1

The formula that describes radioactive decay over time, is the following:

`A=A^{}_0\cdot2^(-t/t_0)`

Where A is the amount of a radioactive element after a time t, if t_0 is the half-life of the given element, for an initial sample A_0.

Solve for A_0, and substitute A=1.3g, t=93.2 and t_0=8.07 to find the initial amount of iodine-131 in the original sample: