Question

Plutonium-239 undergoes alpha decay and has a half-life of 24,000 years. After 72,000 years, how much of an initial 100.0 g sample will remain?

A. none
B. 50.0 g
C. 25.0 g
D. 12.5 g

Answer 1

After 72000 years, the half life would have passed 3 times.

This means that (1/2)^3 = 1/8 of the original sample would remain.

The original sample is 100.0 g, meaning that 1/8 of the sample would be 12.5 g.

So, the answer is D.