Question

There is a 50 g sample of Ra-229. It has a half-life of 4 minutes.

How much will be left after 12 minutes?

Answer 1

Via half-life equation we have:

`A_(final)=A_(initial)((1)/(2))^{(t)/(h) }`

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

`A_(final)=50((1)/(2))^(12)/(4)=50((1)/(2))^(3)=50((1)/(8))=6.25g`

There is 6.25 grams left of Ra-229 after 12 minutes.