Calculating Half-Lives Directions

Calculating Half-Lives


Directions: Here is a table of some isotopes and their half-lives. Use the table to answer the questions that follow.

Isotope	Half-life
Plutonium-238	86 years
Americium-241	433 years
Curium-242	163 days
Berkleium-249	314 days
Californium-249	360 days
Einsteinium-253	20 days
Nobelium-259	1.5 hours
Lawrencium-260	180 seconds

1. If you had a 200 gram sample of Nobelium, how much would remain after 6 hours?

2. If you had a 100 gram sample of Plutonium, how much would remain after 43 years?

3. How much time has passed if 3.75 grams are left of a 60 gram sample of Curium?

4. How much time has passed if 181.25 grams are left of a 725 gram sample of Americium?

5. If you had a 100 gram sample of Einsteinium, how much would be left after 40 days?

6. How many years will have passed if you have 0.5 grams left of an 8 gram sample of Californium?

7. If you had a 5 gram sample of Lawrencium, how much would you still remain in 30 minutes?

8. What happens to the mass of the sample that is no longer there?

9. A rock sample contains 7.5 grams of Californium-249 and and 52.5 grams of the product into which the Californium has changed. How old is the rock?

10. How can you use the half-life of a radioactive sample to figure out how old a fossil is?