Question

The half-life of Palladium-100 is 4 days. After 16 days a sample of Palladium-100 has been reduced to a mass of 6mg. What was the initial mass (in mg) of the sample? What is the mass (in mg) 4 weeks after the start? You may enter the exact value or round to 4 decimal places.

Answer 1

16 days = 16/4 = 4 half-lives

(1/2)^4 = 1/16

1/16 of sample is left after 16 days

6 mg * 16 = 96 mg = amount initially present

4 wks = 4 * 7 = 28 days

28 days / 4 days = 7 half-lives

1/2^7 = .007812

.007812 * 96 mg = .75 mg left after 4 weeks