Chemistry- Physical Science

Question

25.0mg of potassium was isolated in pure form. After one hour, only 3.125mg of the radioactive material was left. What is the half-life of potassium?

Answer 1

25 g ----------- 12.5 g -------------- 6.25 --------3.125 g

For the 25 grams to become 3.125 it took 3 times the half life period which is equal to one hour.

3 half -lives = 60 minutes

half life = 20 minutes