SOLVED

41) Fluorine-18 undergoes positron emission with a half-life of 1.10 × 102 minutes. If a patient is given a 248 mg dose for a PET scan, how long will it take for the amount of fluorine-18 to drop to 83 mg? (Assume that none of the fluorine is excreted from the body.) A) 99 minutes B) 1.74 × 102 minutes C) 1.32 × 102 minutes D) 3.00 × 102 minutes E) 2.11 × 102 minutes 42) Iodine-131 undergoes beta emission with a half-life of 8.02 days. If you start with 44.3 mg of the material, how long will it take for the amount of iodine-131 to drop to 15.3 mg? A) 8.02 days B) 12.3 days C) 23.5 days D) 10.8 days E) 19.8 days 43) The age of an ancient tree trunk is estimated using radiocarbon dating. If the trunk has a C‑14 decay rate that is 34% of what it is in living plants, how old is the trunk? The half-life of C-14 is 5730 years. A) 2.92 × 104 years B) 1.94 × 104 years C) 8.92 × 103 years D) 5.31 × 103 years E) 1.74 × 102 years 44) An archaeologist graduate student found a leg bone of a large animal during the building of a new science building. The bone had a carbon-14 decay rate of 14.8 disintegrations per minute per gram of carbon. Living organisms have a decay rate of 15.3 disintegrations per minute. How old is the bone? A) 53.3 years B) 275 years C) 111 years D) 25 years E) 83 years 45) The nuclide As-76 has a half-life of 26.0 hours. If a sample of As-76 weighs 344 g, what mass of As-76 remains after 538 minutes? A) 67.8 g B) 271 g C) 144 g D) 437 g E) 251 g 46) A geological sample is found to have a Pb-206/U-238 mass ratio of 0.337/1.00. Assuming there was no Pb-206 present when the sample was formed, how old is it? The half-life of U-238 is 4.5 × 109 years. A) 7.3 × 1011 years B) 1.4 × 1010 years C) 2.4 × 1010 years D) 2.1 × 109 years E) 7.1 × 109 years 47) The splitting of a heavy nucleus to form two or more lighter ones is called A) radioactive cleavage. B) nuclear fission. C) nuclear fusion. D) radioactive merge. E) half life. 48) The splitting of the uranium atom is an example of A) radioactive cleavage. B) nuclear fission. C) nuclear fusion. D) radioactive merge. E) half life. 49) Give the goal of the Manhattan project. A) to build an hydrogen bomb B) to build the first particle accelerator at Cornell C) to build an atomic bomb D) to build the first nuclear reactor to generate electricity for Manhattan E) to set up the electrification of Manhattan using DC current 50) The following reaction represents what nuclear process? U + n → Ba + Kr + 3 n A) nuclear fission B) nuclear fusion C) electron capture D) alpha decay E) beta emission