The half-life for a 100-gram sample of radioactive element X is 5 days. How much of element X remains after 10 days have passed?

Question

The half-life for a 100-gram sample of radioactive element X is 5 days. How much of element X remains after 10 days have passed?

A.
25 g

B.
50 g

C.
75 g

D.
100 g

Answer 1

C. 75 g

After 10 days, two half-lives have passed, so only 25% of the original sample remains. Therefore, 75 g of element X remains after 10 days have passed.