What is half-life and how do you calculate it?
Source: various educators and Langhans
1. Fluorine-20 has a half life of 11.6 seconds. If you started with 100 grams of the sample of F-20, how much would remain after 11.6 seconds? After 23.2 seconds?
2. Strontium-90 has a half life of 28 days. If you started with 200 grams of the sample of Sr-90, how much would remain after 56 days?
3. C-14 has a half-life of 5730 years. If a bone originally had a mass of 1000 grams of C-14, how much would remain after 5730 years?
4. Iron-59 has a half-life of 45 days. If the original sample of Fe-59 had a mass of 2000 grams, how much would remain
a. after 45 days?
b. After 90 days?
c. After 135 days?
d. After 180 days?
5. After 1 half-life, what fraction of the sample remains? How much is decayed?
6. After 2 half-life, what fraction of the sample remains? How much is decayed?
7. After 3 half-life, what fraction of the sample remains? How much is decayed?
8. After 4 half-life, what fraction of the sample remains? How much is decayed?
9. After 5 half-life, what fraction of the sample remains? How much is decayed?
10. If I find a 100-g bone that I know is 11460 years old and the half-life of C-14 is 5730, what was the original mass of the bone?
Source: Langhans and various educators
