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? Problem #5: A radioactive isotope decayed to 17/32 of its original mass after 60 minutes. Problem #4: After 24.0 days, 2.00 milligrams of an original 128.0 milligram sample remain. 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. 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. 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. If you currently have 73.3 g of P-32, how much P-32 was present 4 days ago?Įxample #8: If a sample contains 144 atoms of Au-179 (half-life = 7.5 s), approximately how many such atoms were present 30 seconds earlier?Įxample #9: Find the half-life of an element which decays at a rate of 3.402% per day.Įxample #10: The half-life of In-111 is 0.007685 years how long (in hours) would it take for the amount of In-11 to decrease to 43.24% of its initial amount?īonus Example: A scrap of paper taken from a Dead Sea scroll was found to have a C-14/C-12 ratio of 0.795 times than found in plants living today. How many grams did you have 100 years ago?Įxample #7: P-32 is radioactive isotope with a half-life of 14.3 days. How old is an object that has lost 60% of its carbon-14?Įxample #6: An element has a half-life of 25 years. The percentage of carbon-14 present in the remains of plants and animals can be used to determine age. What is the half-life of this radioactive isotope?Įxample #4: Calculate the half life of a sample of ChemTeamium which decays from 27.5 g to 0.598 g in a period of 574 years.Įxample #5: The radioactive element carbon-14 has a half-life of 5730. ChemTeam: Half-Life: Examples and Problems only Half-Life: Examples and Problems onlyĮxample #1: How many years will it take for 88.0 grams of tritium to decay to an 11.0 gram sample? (The half-life of tritium is 12.3 years.)Įxample #2: How many years will it take for 84.0 grams of tritium to decay to a 23.5 gram sample? (The half-life of tritium is 12.3 years.)Įxample #3: A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 in 60.0 hr.
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