Sample Questions - Chapter 26

Nuclear Chemistry

Examples of
Multiple Choice Questions

1.: The "magic numbers" for atoms are; (a) numbers of electrons that confer atomic stability.; (b) numbers of protons and/or neutrons that confer nuclear stability.; (c) n/p ratios that confer nuclear stability.; (d) atomic masses that confer nuclear stability.; (e) atomic masses that indicate fissile isotopes.
2.: The actual mass of a ³⁷Cl atom is 36.966 amu. Calculate the mass defect (amu/atom) for a ³⁷Cl atom.; (a) 0.623 amu; (b) 0.388 amu; (c) 0.263 amu; (d) 0.341 amu; (e) none of these
3.: The mass defect for an isotope was found to be 0.410 amu/atom. Calculate the binding energy in kJ/mol of atoms. (1 J = 1 kgm²/s²); (a) 3.69 x 10¹⁰ kJ/mol; (b) 1.23 x 10²⁰ kJ/mol; (c) 3.69 x 10¹³ kJ/mol; (d) 1.23 x 10³ kJ/mol; (e) 1.23 x 10²³ kJ/mol
4.: Calculate the binding energy per nucleon (in units of MeV) for ⁹Be, for which the atomic mass is 9.01219 amu. Particle masses in amu are: proton = 1.007277; neutron = 1.008665; electron = 0.0005486. Conversion factor for E = mc² is 931 MeV/amu.; (a) 6.46 MeV; (b) 6.33 MeV; (c) 6.23 MeV; (d) 11.39 MeV; (e) 56.93 MeV
5.: Which isotope below has the highest nuclear binding energy per gram? No calculation is necessary.; (a) ⁴He; (b) ¹⁶O; (c) ³²S; (d) ⁵⁵Mn; (e) ²³⁸U
6.: Which of the following statements is incorrect?; (a) Mass defect is the amount of matter that would be converted into energy if a nucleus were formed from initially separated protons and neutrons.; (b) Nuclear binding energy is the energy released in the formation of an atom from subatomic particles.; (c) Nuclei with highest binding energies are the most stable nuclei.; (d) Einstein postulated the Theory of Relativity in which he stated that matter and energy are equivalent.; (e) Mass number is the sum of all protons and electrons in an atom.
7.: A positron has a mass number of _____, a charge of _____, and a mass equal to that of a(an) _____.; (a) 0, 1+, proton; (b) 1, 2+, proton; (c) 0, 1+, electron; (d) 1, 2+, electron; (e) 0, 0, proton
8.: Emission of which one of the following leaves both atomic number and mass number unchanged?; (a) positron; (b) neutron; (c) alpha particle; (d) gamma radiation; (e) beta particle
9.: Which type of radiation is the least penetrating?; (a) alpha; (b) beta; (c) gamma; (d) x-ray; (e) neutron
10.: A radioisotope of argon, ³⁵Ar, lies below the "band of stability: (n/p ratio too low). One would predict that it decays via _____.; (a) neutron emission; (b) beta emission; (c) positron emission; (d) alpha emission; (e) fission
11.: A Geiger-Muller tube is a _____ .; (a) gas ionization detector; (b) cloud chamber; (c) fluorescence detector; (d) spectrophotometer; (e) photographic detector
12.: The half life of ²³¹Pa is 3.25 x 10⁴ years. How much of an initial 10.40 microgram sample remains after 3.25 x 10⁵ years?; (a) 0.0102 micrograms; (b) 0.240 micrograms; (c) 2.18 micrograms; (d) 0.0240 micrograms; (e) 1.04 micrograms
13.: Consider the case of a radioactive element X which decays by electron (beta) emission with a half-life of 4 days to a stable nuclide of element Z. Which of the following statements is CORRECT?; (a) After 8 days the sample will consist of one-fourth element Z and three-fourths element X.; (b) Element Z will weigh exactly the same as element X when decay is complete (weighed to an infinite number of significant figures).; (c) 2.0 g of element X is required to produce 1.5 g of element Z after 8 days (to 2 significant figures).; (d) If element X as an atomic number equal to n, then element X has an atomic number equal to n-1.; (e) None of the above.
14.: Carbon-11 is a radioactive isotope of carbon. Its half-life is 20 minutes. What fraction of the initial number of C-11 atoms in a sample will have decayed away after 80 minutes?; (a) 1/16; (b) 1/8; (c) 1/4; (d) 7/8; (e) 15/16
15.: How old is a bottle of wine if the tritium (³H) content (called activity) is 25% that of a new wine? The half-life of tritium is 12.5 years.; (a) 1/4 yr; (b) 3.1 yr; (c) 25 yr; (d) 37.5 yr; (e) 50 yr
16.: A Geiger counter registered 1000 counts/second from a sample that contained a radioactive isotope of polonium. After 5.0 minutes, the counter registered 281 counts/second. What is the half-life of this isotope in seconds?; (a) 87; (b) 110; (c) 164; (d) 264; (e) 2.18
17.: The ¹⁴C activity of some ancient Peruvian corn was found to be 10 disintegrations per minute per gram of C. If present-day plant life shows 15 dpm/g, how old is the Peruvian corn? The half-life of ¹⁴C is 5730 years.; (a) 1455 years; (b) 1910 years; (c) 3350 years; (d) 3820 years; (e) 9080 years
18.: Which of the following describes what occurs in the fission process?; (a) A heavy nucleus is fragmented into lighter ones.; (b) A neutron is split into a neutron and proton.; (c) Two light nuclei are combined into a heavier one.; (d) A proton is split into three quarks.; (e) A particle and anti-particle appear in an area of high energy density.
19.: Which of the following statements about nuclear fission is always correct?; (a) Very little energy is released in fission processes.; (b) Nuclear fission is an energetically favorable process for heavy atoms.; (c) Due to its instability, ⁵⁶Fe readily undergoes fission.; (d) In fission reactions, a neutron is split into a proton and an electron.; (e) All nuclear fission reactions are spontaneous.
20.: Which one of the following would be most likely to undergo thermonuclear fusion?; (a) ²H; (b) ⁴He; (c) ⁵⁶Fe; (d) ¹⁴¹Ba; (e) ²³⁵U
21.: Which one of the following statements about nuclear reactions is false?; (a) Particles within the nucleus are involved.; (b) No new elements can be produced.; (c) Rate of reaction is independent of the presence of a catalyst.; (d) Rate of reaction is independent of temperature.; (e) They are often accompanied by the release of enormous amounts of energy.
22.: Complete and balance the following equation. The missing term is _____ . ²³⁹Pu + alpha particle _____ + neutron; (a) 2 ¹¹⁵Ag; (b) 2 ¹⁰⁶Rh; (c) ²³⁵U; (d) ²³³Pa; (e) ²⁴²Cm
23.: When ⁵⁹Cu undergoes positron emission, what is the immediate nuclear product?; (a) ⁵⁹Ni; (b) ⁵⁸Ni; (c) ⁵⁸Cu; (d) ⁵⁹Zn; (e) ⁵⁸Zn
24.: As a result of the process of electron capture ("K-capture") by ²¹¹At, the new isotope formed is:; (a) ²¹⁰At; (b) ²¹²At; (c) ²¹¹Po; (d) ²¹¹Rn; (e) ²⁰⁷Bi
25.: When ²³⁵U is bombarded with one neutron, fission occurs and the products are three neutrons, 94Kr, and _____ .; (a) ¹³⁹Ba; (b) ¹⁴¹Ba; (c) ¹³⁹Ce; (d) ¹³⁹Xe; (e) ¹⁴²I

Answers:

1. (b) 2. (d) 3. (a) 4. (a) 5. (d) 6. (e) 7. (c) 8. (d) 9. (a) 10. (c) 11. (a) 12. (a) 13. (c) 14. (e) 15. (c) 16. (c) 17. (c) 18. (a) 19. (b) 20. (a) 21. (b) 22. (e) 23. (a) 24. (c) 25. (a)

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