Question 12 (2 points) A sample contains 4.01022 atoms of the sodium isotope 21 Na. The half-life of this 11 nuclide 23 s. How many atoms will be present in this sample after 10 minutes? Question 13 (2 points) The mass of the isotope 25 Na is 24.99 u. How many atoms are in a sample of 25 whose mass is 0.5 g? 11 Na Question 16 (2 points) Calculate the binding energy BE associate with the increase in mass for the reaction: 12 C 11C + on. Use the masses given as follows: -> 0 1/c:12.0000 1C:11.011432 #: 1.008665 Question 14 (3 points) What is the activity of a 0.50 g of sodium isotope 25 Na at time t = 1000 s if its activity at t = 0 is 1.3921020 s-1? You can use the number of atoms obtained from the above problem directly. One example of a nuclear fission reaction involving slowly moving neutrons is 95 42 235U+ on 35 Mo+ 139 La + 2n. What is the total energy (in MeV) released of 57 the reaction? Use the masses given as follows: 235 92:235.0439 95 42 Mo:94.9058; 139 La:138.9061; 57 on: 1.0087