# The half-life of cesium-137 is 30.2 years. If the initial mass of a sample of cesium-137 is 1.00 g, how much will remain after 30.2 years?

##### 1 Answer

Nov 22, 2016

0.500 grams

#### Explanation:

The half-life is the amount of time it takes for a given sample to lose half of the original amount.

In this case, the original amount is 1.00 grams.

The half-life is 30.2 years.

The elapsed time is 30.2 years.

Thus, one half-life has elapsed. Therefore you have lost half the original mass. You have 0.500 grams remaining.

Note that after another 30.2 years you will ** not ** lose the remaining amount! Instead, you will lose half of the original amount, so you will lose another 0.250 grams, leaving 0.250 grams behind.