Half life - Revsworld

1. What is the half-life of 210 Bi if 25% of a sample
of 210 Bi decays in 2.079 days?
(A)0.50 days (D)2.5 days
(B) 0.75 days (E) 5.0 days
(C) 1.05 days
2. What fraction of a sample of polonium, 218 Po,
remains after one hour if 218 Po has a half-life of
3 minutes?
(A) 1
2 20
(B) 1
20 2
(C) 1
2 × 20
(D) 1
20
(E) 1
20 ^ 2
3. A sample of an ore contains 100. micrograms of
radioactive phosphorus–32 with a half-life of
14.3 days. How many micrograms of 32 P remain
in the sample after 28.6 days? The symbol for
the microgram is mg.
(A)0.00 mg
(D)50.0 mg
(B) 12.5 mg
(E) 75.0 mg
(C) 25.0 mg
4. Nickel–58 has a half–life of 36.0 hours. Starting
with 2.00 gram of this isotope, how much would
remain at the end of 144 hours?
(A)0.0625 g (D)0.500 g
(B) 0.125 g
(E) 1.00 g
(C) 0.250 g
5. The activity of a sample of La–140 goes from
640. cpm to 40.0 cpm in 160. hours. Which is its
half-life?
(A)10.0 h
(D)640. h
(B) 40.0 h
(E) 2560. h
(C) 160. h
6. Mendeleevium–256 emits at a rate of 100. dps
after 2.00 hours of experimenting. If the
half–life is 30.0 minutes, what was the original
count rate in dps?
(A)100.
(D)1,600.
(B) 400. (E) 3.28 × 10 6
(C) 1500.
7. Indium-124 is a radioactive isotope. If you
begin with a 500. gram sample of pure 124 In, and
only 62.5 grams remain after 12.0 seconds, what
is the half-life of 124 In?
(A)1.00 second (D)4.00 seconds
(B) 2.00 seconds (E) 6.00 seconds
(C) 3.00 seconds
8. The half life of 116 Sb is 15 minutes. If you begin
with a pure sample of 116 Sb, how long will it
take for you to have 3.125 % left?
(A)30 minutes (D)75 minutes
(B) 45 minutes (E) 90 minutes
(C) 60 minutes
9. The half life of 133 Cs is 6.5 days. If you begin
with a pure sample of 133 Cs, what percent is left
after 26 days?
(A)3.13 % (D)12.5 %
(B) 5.00 % (E) 25.0 %
(C) 6.25 %
10. The radioisotope I-131 has a half life of
approximately 8.0 days. How long would it take
for 87.5% of it to decay?
(A)4.2 days
(D)16 days
(B) 8.3 days
(E) 24 days
(C) 12 days
11. Carbon-14 has a half-life of about 5700 years.
A sample of 1.0 g is determinded to have
originally weighed 32 g. Approximately how
old is this sample?
(A)5700 years (D)28,500 years
(B) 11,400 years (E) 34,200 years
(C) 22,800 years

17. What is the missing product in the reaction
12. 131 I has a half-life of about 8.1 days. If a lab
(E) 231
93 Np
purchased a sample weighing 10. mg 24.3 days below?
days ago, about how much is left?
234
(A)10. mg
(D)0.6 mg
90 Th → 0 +1β ~ ?
(B) 2.5 mg
(E) 0.3 mg
(A) 234
89 Ac
(C) 1.3 mg
(B) 234
90 Th
(C) 230
90 Ac
13. The half-life of 42 K is about 12 hours. It takes
2.0 days for a sample to arrive. How much
(D) 230
89 Ac
(E) 234
91 Pa
should be sent if 5.0 g are needed at the
destination?
18. In the decay series that starts with Fr-222, the
(A)160. g
(D)20. g
first step consists of a beta decay. The next
three steps are alpha particle decay. The final
(B) 80. g
(E) 5.0 g
step is another beta particle decay. What is the
(C) 40. g
product of this decay series?
(A)Pb-212
(D)Bi-210
14. A certain radioactive element undergoes beta
decay to become 214 Bi. What could this be?
(B) Bi-212
(E) Pb-210
(A) 215 Bi
(C) Po-210
(B) 214 Po
(C) 215 19. Base your answer to the following question on
Po
(D) 215 the elements below.
Pb
(E) 214 Pb
(A) Pb
15. Radioactive plutonium, 214
(B) Cd
84
Pu, emits an alpha
(C) U
particle and changes to a new element, “X”. This
(D) Ga
new element emits a beta particle and is
(E) Ni
converted to element “Y”. Which are
representations of elements X and Y?
(A) 210 212
81
X and
83 Y
Which is the end product of the decay of Ra-
226?
(B) 212 210
82 X and 81 Y
(C) 212 211
80
X and
81 Y
(A)A
(D)D
(D) 210 210
80
X and
81 Y
(B) B
(E) E
(E) 210 210
82
X and
83 Y
(C) C
16. Uranium, 235
20. Which of the following choices correctly lists
92
U, emits an alpha particle
alpha particles, beta particles, and gamma rays
producing a daughter nucleus, X. X then
in increasing energy?
disintegrates, emitting a beta particle, and
producing its daughter element, Y. Substance Y
(A)Alpha particles>beta particles>gamma rays
is
(B) Gamma rays>beta particles>alpha particles
(A) 232
89 Ac
(C) Alpha particles>gamma rays>beta particles
(B) 233
91 Pa
(D)Gamma rays>alpha particles>beta particles
(C) 237
93 Np
(E) Beta particles>gamma rays>alpha particles
(D) 231
91 Pa

21. What happens to the mass number and the
atomic number of an element when it undergoes
beta decay?
(A)Neither the mass number nor the atomic
number change.
(B) The mass number does not change and the
atomic number increases by 1.
(C) The mass number does not change and the
atomic number decreases by 2.
(D)The mass number decreases by 4 and the
atomic number decreases by 2.
(E) The mass number increases by 2 and the
atomic number increases by 1.
22. The nuclide 140
56
Ba is radioactive and decays by
loosing 1 beta (î – ) particle. The product formed
is
(A) 140
55 Cs
(B) 140
56 Ba
(C) 141
56 Ba
(D) 140
57 La
(E) 141
57 La
23. What sort of radiation would be expected for 8 5 B?
(A)alpha emission
(B) beta emission
(C) gamma emission
(D)positron emission
(E) none, it is a stable nucleus
24. The radioactive decay 3 H to 3 He occurs by the
process of
(A)beta particle emission
(B) positron emission
(C) alpha particle emission
(D)gamma ray emission
(E) gamma ray absorption
25. Which of the following has the greatest mass?
(A)An alpha particle (D)A positron
(B) A beta particle (E) A hydrogen nucleus
(C) A gamma ray
26. When 12 N decays by positron emission, it
becomes?
(A) 13 N
(B) 12 N
(C) 13 C
(D) 12 C
(E) 8 B
27. If the neutron to proton ratio for an isotope is
too high, the nucleus will achieve stability by
(A)beta decay (D)electron capture
(B) alpha decay (E) gamma decay
(C) positron decay
28. Base your answer to the following question on
the atomic numbers given below.
(A) 9
(B) 10
(C) 46
(D) 51
(E) 84
Which element has no stable isotopes?
(A)A
(D)D
(B) B
(E) E
(C) C
29. Base your answer to the next question on the
following elements.
(A) Germanium
(B) Polonium
(C) Fluorine
(D) Iron
(E) Calcium
Has no stable isotopes.
(A)A
(B) B
(C) C
(D)D
(E) E

Answer Key
1. E
2. A
3. C
4. B
5. B
25. A
26. D
27. A
28. E
29. B
6. D
7. D
8. D
9. C
10. E
11. D
12. C
13. B
14. E
15. E
16. D
17. A
18. D
19. A
20. B
21. B
22. D
23. D
24. A