Question

A sample of Francium-212 will decay to one sixteenth of its original amount after 80 minutes. What is the half-life of Francium-212.

Answer 1

20 minutes.

The sample would lose one half the quantity of francium in each half-life.

`1/16 = 1/2^(4) = 1/2 *1/2 *1/2 *1/2`

Thus a mass decrease by a factor of 16 would correspond to a period of four half-lives. It took 80 minutes for the sample to lose all these francium, therefore

`t_(1/2) = 80/4 = 20` minutes.