Question

The half life of Po-218 is three minutes. How much of a 2.0 gram sample remains after 15 minutes? Suppose you wanted to buy some of this isotope, and it required half an hour for it to reach you. How much should you order if you needed to use 0.10 gram of this material?

Answer 1

After 15 minutes :

M = M₀ (1/2)^(t/T)

M = 2 (1/2)^(15/3)

M = 0.0625 gr

In order to get 0.1 gr :

M = M₀ (1/2)^(t/T)

0.1 = M₀ (1/2)^(30/3)

0.1 = Mo / 1024

Mo = 102.4 gr