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# Half Life Worksheet - DOC by wem93755

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```									Chemistry- Half-life Worksheet

Name ___________________________ Date ____________ Period _____________

1. Phosphorus-32 is used to treat some diseases of the bone. Its half-life is 14 days. Find the time it would take
for a sample of phosphorus-32 to decay from 100.0 g to 25.0g.

TIME                       HALF-LIFE                     AMOUNT                FRACTION REMAINING

2. What would be the remaining fraction of the sample in question 1 above after 42 days?

3. A certain isotope has a half-life of 20 days. How long would it take for a sample of this isotope to decay from
10,000 cpm (counts per minute) to 2500 cpm?

TIME                       HALF-LIFE               AMOUNT (ACTIVITY)           FRACTION REMAINING

4. What would be the activity of the sample in question 2 after 60 days?

5. Vanadium-49 has a half-life of 330 days. The initial mass of a 2g sample decreases to what fraction after 4
half-lives?

TIME                       HALF-LIFE                     AMOUNT                FRACTION REMAINING

6. Chromium-48 has a half-life of about 24 hours. If the initial activity of a sample of chromium-48 is 3000,
what would the activity be after 96 hours?

TIME                       HALF-LIFE                     AMOUNT                FRACTION REMAINING
7. Iodine-131 transmutes to Xenon during the decay process. How much Xe is produced after 400 grams of
Iodine-131 is allowed to decay for 24 days? The half-life of Iodine-131 is 6 days.

TIME                       HALF-LIFE                        AMOUNT              FRACTION REMAINING

8. How much time would have to elapse before the radioactivity in a piece of wood, due to carbon-14, would drop
from 16 counts per minute to 2 counts per minute? (The half-life of carbon-14 is 5730 years).

TIME                       HALF-LIFE                        AMOUNT              FRACTION REMAINING

9. Iron-55 has a half-life of 45 days. If a piston ring had an initial activity of 10,000 counts per second what
would the activity be after 135 days.

TIME                       HALF-LIFE                        AMOUNT              FRACTION REMAINING

10. How much time would have to elapse in order for the activity of the piston ring in problem 9 to drop from
10,000 counts per second to 625 counts per second?

TIME                       HALF-LIFE                        AMOUNT              FRACTION REMAINING

Write the nuclear equation for the decay of the following isotopes:

11.     uranium-238

12.     cesium-137

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