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Initially, a particular sample has a total mass of 240 grams and contains 512 x 1010 radioactive nuclei. These radioactive nuclei have a half life of 1 hour. (a) After 4 hours, how many of these radioactive nuclei remain in the sample (that is, how many have not yet experienced a radioactive decay)? Note that you can do this problem without a calculator. 32 x 1010 radioactive nuclei (b) After that same amount of time has elapsed, what is the total mass of the sample, to the nearest gram? 15 X g A single atom of cesium-133 has a mass, in atomic mass units, of 132.90545193 u. (a) Determine the mass defect, in atomic mass units. u (b) Determine the total binding energy, in MeV. MeV (c) Determine the average binding energy per nucleon. MeV Fluorine-18 decays through a beta-plus decay process. Use the table to find the relevant masses for this decay, and calculate the energy (in MeV) released by the decay of one such atom. You can neglect the mass of the neutrino that is one of the decay products. A supply of fluorodeoxyglucose (FDG) arrives at a positron emission tomography clinic at 8 am. At 2 pm, when you arrive at the clinic to get a PET scan, the activity level of the FDG has dropped significantly because of the 110 minute half-life of the radioactive fluorine. Considering equal masses of FDG at 8 am and 2 pm, by what factor has the activity level been reduced by 2 pm? Note that another way to ask the same question is to say that we're looking for the ratio of the initial activity to the activity at 2 pm. The level has been reduced by a factor of . After exactly 5 hours, the activity level of a sample of a particular radioactive isotope, which decays into a stable isotope, has fallen to 30.0% of its initial value. Calculate the half-life of this isotope. L