Honors Chemistry I
Atomic Theory / Nuclear Chemistry
Practice Test Solution Set
1. 1.37 x 104 yrs An organic artifact is analyzed and found to contain 18.98% of the C-14 that it should have had originally. Using the half-life listed on your periodic table for C-14, what is the approximate age of this artifact?
0.693 = k(5730 yrs) k = 1.21 x 10-4 yrs-1
ln(100 / 18.98) =1.21 x 10-4 yrs-1 t => t = 13733.7 yrs.
2. 235 How many nucleons are there in a radioactive nuclide of Th-235?
3. C Which of the following is a piece of antimatter?
A) alpha; B) beta; C) positron; D) gamma; E) deuteron; F) neutron; G) both C & E.
4. A If the Si-33 nuclide is noted for its unusually high neutron-to-proton ratio, what type of radioactive decay does it undergo?
A) beta decay; B) positron emission; C) alpha decay; D) K (electron) capture
5. B If the Li-4 nuclide is noted for its unusually low neutron-to-proton ratio, what type of radioactive decay does it undergo?
A) beta decay; B) positron emission; C) alpha decay; D) K (electron) capture
6. D If the Tl-201 nuclide, which is considered a heavy nuclide, is noted for its unusually low neutron-to-proton ratio, what type of radioactive decay does it undergo?
A) beta decay; B) positron emission; C) alpha decay; D) K (electron) capture
7. C If the At-213 nuclide is noted because it lies beyond the “belt of stability”, what type of radioactive decay does it undergo?
A) beta decay; B) positron emission; C) alpha decay; D) K (electron) capture
8. F Which of the following nuclides would be predicted to be unusually stable, based on the “magic numbers” that it displays?
A) Ca-40; B) Pb-208; C) Bk-247; D) Os-190; E) At-212; F) both A and B
9. Geiger counter What is the name of the device that detects the amount of radiation emanating from a source of radioactive material? Unfortunately, it does not indicate the type of radiation?
10. C What is the name for the heaviest isotope of hydrogen?
A) ozone; B) deuterium; C) tritium; D) protium; E) alpha; F) beta
11. B Which of the following has 20 protons and 18 electrons?
A) S2+; B) Ar2-; C) Ca+2; D) K+1; E) S2-
-2-
12. D An alpha particle is essentially:
A) an electron; B) a positron; C) a proton; D) a helium nucleus.
Complete the following reactions
13. Fr-224 Ac-228 à ?? + a
14. Sr-90 ?? + Li-7 à Nb-97 + g
15. b Ce-140 + ?? à Ba-138 + D
16. a N-14 + ?? à O-17 + p
......
Answer the following questions based on the -3 anion of an isotopic form of antimony: Sb-122
17. 122 What is the A number for this nuclide?
18. 51 What is the Z number for this nuclide?
19. 51 What is the number of protons in the anion form of this metalloid?
20. 54 What is the number of electrons in the anion form of this metalloid?
21. 71 What is the number of neutrons in the anion form of this metalloid?
22. 122 What is the number of nucleons in a nuclide of this isotope?
Complete the following nuclear reactions:
23. Md-258 Es-256 ( D , b ) ____?_____
24. Th-231 ?? ( T , 2 n ) Pa-232
25. b+ Rn-223 ( a , ? ) Fr-227
-3-
26. Fm-255 Nobelium-259 undergoes spontaneous radioactive decay by alpha emission. What is the resulting nuclide?
102No259 à 2He4 + 100Fm255
27. 1.47 x 10-3 day-1 What is the decay rate constant of Es-252 if it has a half-life of 472 days?
0.693 = k (472 days) k = 1.47 x 10-3 day-1
28. 0.965 hr. How many hours does it take for a 6.000-gram sample of Fr-212 to decay until only 0.750 grams remains behind? The half-life of Fr-212 is 19.3 minutes.
6.000 à 3.000 à 1.500 à 0.750 => [3(19.3 min)]/60 = 0.965 hr
or ln(6.000 / 0.750) = 2.08 = (0.0359 min-1)t => t = 57.9 min = 0.965 hr
29. 37.0 g. How many grams of Md-258 were initially present if only a 2.82-gram sample remains after 205 days? It has a half-life of 55.2 days.
0.693 = k(55.2 days) = 0.01255 days-1
ln( X / 2.82) = (0.01255 days-1)(205 days) = 2.57
X = 37.0 g.
30. Goldstein Who observed rays traveling in the opposite direction of the cathode rays? (He called them canal rays, which we now know them to have been protons.)
31. 27.77% A certain element is known to contain two stable isotopes M-203 and M-205. If the atomic mass of 203 is 203.1022 amu and the atomic mass of M-205 is 205.1123 amu, while the average atomic mass for this element is known to be 203.6604 amu, what is the percent abundance of the heavier isotope?
203.6604 = 205.1123 X + 203.1022 (1.000 - X)
0.5582 = 2.0101 X => X = 0.277697
32. 66.55% Another element is known to contain three stable isotopes P-222, P-225 and P-227. The atomic mass of P-222 is 222.2352 amu, the atomic mass of
P-225 is 225.3123 amu, and the atomic mass of P-227 is 227.8845 amu. The average atomic mass for this element is known to be 224.7455 amu, and the lightest isotope is three times as abundant as the heaviest one. What is the percent abundance of the P-225 isotope?
224.7455 = 222.2352(3X) + 227.8845(X) + 225.3123(1.000 - 4X)
-0.5668 = -6.6591X X = 0.08512
P-225 = 1-4X = 0.6595