Radioactivity and Nuclear Chemistry

Practice Exam Chemical Kinetics Name (last)________________(First)______________________

Read all questions before you start. Show all work and explain your answers to receive full credit. Report all numerical

answers to the proper number of significant figures. By signing your signature above you agree that you have worked alone

and neither give nor received help from any source. Keep your eyes on your own paper at all times

Chapter 21 Nuclear Chemistry 1 Radioactivity 2 Patterns of Nuclear Stability 3. Nuclear Transmutations 4. Rates of Radioactive Decay

5. Detection of Radioactivity 6. Energy changes in Nuclear Reactions 7. Nuclear Fission /Fusion 8. Biological effects

1 If the half-life of a hypothetical isotope is 5 hr, how much remains if 20.0g decays after 15 hr? a) 2.50 g b) 5.00 g c) 6.67 g d) 10.0 g e) no right answer 20 g --5 hrs 10 g --5 hrs 5.0 g --5 hrs 2.5 g (Total elapse time = 15 hrs) 2 When a neutron is transformed into a proton what else is emitted

a) alpha b) position c) 1H d) electron e) none of these 16n → 11p + 0-1e 3 Which of the following transformations is not an alpha emission? a) 241Am → 237Np b) 225Ac → 221Fr c) 14C → 14N d) 218Po → 214Pb e) all possible 146C → 147N + 0-1e 4 The three main radiation involved in radioactivity are alpha, beta and gamma radiation's. Discuss the differences for

each radiation, their penetrating power and the affect each has on living tissues.

5 A hospital needs radium for chemotherapy. The radiologist places an order to Isotopes-R-Us for 709 mg of 223RaCl2 at 11:00 pm, Monday, but the hospital does not receive the compound until 5:00 pm, Tuesday. How much should the

Radiologist pay the company upon receiving the compound ? Market value of 223Ra (t1/2 = 280.8 hr.) is $50,000 per gram based on radium content.

6 Neptunium-241 forms a stable isotope through a transformation series that involves the following successive particles

emissions: α, β, β, α, α, α, α, α, β, β, α, β, β, α (note there are 14 emission processes). Write the disintegration equation for the series

7 A long cherished dream of alchemists was to produce gold from cheaper, abundant elements. This dream was finally

realized when 198Hg was converted to gold by neutron bombardment. Write the complete balanced equations for this process. (Note that a series of process may occur in this transmutation. Furthermore, gold has only one isotope).

8 Radiochemists have proposed that a natural radioactive decay series probably began with 243Am, but all of this nuclide had decayed within the first few million years of the Earth's existence. This series would have begun by emission of an a particle, then a b particle, then two more a particles. Write a balanced nuclear equation for each step.

9 A sample of sodium-24 was administered to a patient to test for faulty blood circulation by comparing the radioactivity

reaching various parts of the body. What fraction of the sodium-24 nuclei would remain undecayed after 24.0 hr ? The half-life is 15.0 hr. If a sample contains 5.0 mg of 24Na, how many mg remain after 24.0 hr?

10 Find the change of mass (in grams) resulting from the release of heat when 1 mol SO2 is formed from the elements. S(s) + O2(g) → SO2 (g) ΔH = -297 kJ

11 The naturally occurring isotope rubidium-87 decays by beta emission to strontium-87. This decay is the basis of a

method for determining the ages of rocks. A sample of rock contains 102.1 mg 87Rb and 5.3 mg 87Sr. What is the age of the rock? The half-life of rubidium-87 is 4.8•1010 yr.

12 Write nuclear equations for the following radioactive decays: i) beta decay of radium -228 ii) alpha decay of polonium -210 iii) electron capture of lanthanum-137

13 The atomic masses of three isotopes of aluminum are: 26Al - 25.9869, 27Al - 26.9815, 28Al - 27.9819. i) calculate the

binding energy per nucleon in MeV for each of these isotopes of aluminum. ii) Two of these nuclides are radioactive and the third one is stable. Based on your answer to part i) which isotopes are unstable ?

14 How many a and b particles are emitted in the decay series that begins with 237Np and finally produces the stable isotope 209Bi ?