Homework Problems in Nuclear Chemistry

 

1. To the best of your ability, describe the nucleus of an atom.

 

2. Compare β- and electrons.

 

3. Calculate the binding energy (in MeV and J/mol) and binding energy per nucleon for 136 Xe (135.9072 daltons),  208Pb (207.9766 daltons) and 28Si (27.97693 daltons).  Which nucleus is the most stable?

 

4. Write the nuclear reactions for the following

 

a) the α decay of 238Pu         b) the negatron decay of 60Co

 

c) the positron decay of 11C               d) the electron capture decay of 208Bi

 

e) the neutron-induced fisson of 235U into 144Ba, ? and two neutrons

 

f) 238U(12C, 4n)246Cf                               g) 238U(n,γ)239U

 

5.  Radioactive 222Rn is known to accumulate in basement of buildings and constitute a health risk.

a) What is the parent primary natural radionuclide the produces the 222Rn?

b) Write the reaction for the nuclear decay of radon-222.

c) Why are none of the intermediate radionuclides (or the parent) considered a health risk?

 

6. Predict a reasonable decay mode for each of the following.  Write the decay reaction and explain your reasoning.

 

a) 243Am b) 17F                      c) 49Ca                    d) 181Ir

 

7. Plutonium-238 has been used as a source to power heart pacemaker batteries.  Its half-life is 87.74 year.  Calculate the activity in units of curies for 0.25 g of pure plutonium-238 used is a pacemaker battery.  Why is it a good power source in a pacemaker?

 

8. What is the activity, in Ci, of a γ-ray source that emits a single 1.67 MeV γ-ray per disintegration, if the dose received at a distance of 1.0 m from the source is 337 mrad/h?

 

9. A 60Co source (t1/2 = 5.2714 y)  that had an initial activty of 5.0 Ci has been in a laboratory for 15 years.  Calculate the exposure rate 3.0 ft from the source.  Assume there is no shielding around the source and remember to account for decay of the source. The value of n is 1 for both the the  60Co γ-rays (which have energies of 1.3325 MeV and 1.1732 MeV) and the β-ray has an energy of 0.318 MeV. 

 

10.  What quarks would make up π-?  Hint: p + π- <==> n

 

11.  For stable isotopes, the N/Z ratio (neutrons/protons) is about one for light elements and increases as the elements get heavier.  Use the semi-empirical binding energy equation to qualitatively explain this.

 

12.  Why can you get energy from both fission and fusion.  Under what circumstances will this statement be true?

 

13. Xenon-135 has a huge neutron capture cross section.  Explain.

 

Solutions