Answer to Question #144176 in Chemistry for Stephanie

Question

The radioisotope cesium-137 has a half life of 25.00 years. A sample decays at a rate of 192.0 counts per minute (192.0 cpm) in the year 2000. In what year will the decay rate be 3.000 cmp?

Answer 1

It will take 6 half-lives to reach 3 counts per minute.

Multiplying: 25 x 6 = 150 years (The length of time it will take)

2000 + 150 = 2150 - this is the year in which the decay rate will be 3 counts per minute.