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?
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