If the half-life is 23.9 hours, how much will be present at the end of one day? Two days? Seven days? Problem #8: At time zero, there are 10.0 grams of W-187. How much time will elapse for this sample to be considered gone?
A radioactive sample is considered to be completely decayed after 10 half-lives. Problem #7: Fermium-253 has a half-life of 0.334 seconds. Problem #6: How long will it take for a 40.0 gram sample of I-131 (half-life = 8.040 days) to decay to 1/100 its original mass? N = 0.91254 (this is how many half-lives have elapsed) Solution: 17/32 = 0.53125 (this is the decimal amount that remains)
Problem #5: A radioactive isotope decayed to 17/32 of its original mass after 60 minutes. Video: An Alternate Solution to the Above Problem What is the half-life of the sample?Ģ) How many half-lives must have elaspsed to get to 0.015625 remaining? Problem #4: After 24.0 days, 2.00 milligrams of an original 128.0 milligram sample remain. In addition, note that the question asked for the amount that decayed, not the amount that remaning. Note that the length of the half-life played no role in this calculation. How many grams of a 10.0 gram sample would have decayed after exactly three half-lives? Problem #3: Os-182 has a half-life of 21.5 hours. (1/2) 5.56 = 0.0213 (the decimal fraction remaining after 5.56 half-lives) If one had 6.02 x 10 23 atoms at the start, how many atoms would be present after 20.0 days? Problem #2: Pd-100 has a half-life of 3.6 days. (1/2) 3 = 0.125 (the amount remaining after 3 half-lives) If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed? Problem #1: The half-life of Zn-71 is 2.4 minutes. ChemTeam: Half-Life Problems #1 - 10 Half-Life Problems #1 - 10 Ten Examples Problems involving carbon-14 Probs 11-25 Problems involving uranium-238 Probs 26-40 Examples and Problems only (no solutions) Return to Radioactivity menu
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