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Nuclear Chemistry
Practice Problems
You have 10 minutes. You may not use a calculator. You may use your AP periodic table. For each question,
circle the letter of your choice.
1. When
is:
decays, it emits 2 α particles, then a β particle, followed by an α particle. The resulting nucleus
2. The formation of
from
A. electron capture
B. α decay
C. β decay
D. positron decay
E. γ decay
occurs by:
3. Which of the following lists the types of radiation in the correct order of increasing penetrating power?
A. α, γ, β
B. β, α, γ
C. α, β, γ
D. β, γ, α
E. γ, β, α
4. What is the missing product in the following nuclear reaction?
5. Which of the following statements are correct concerning β particles?
I.
They have a mass number of zero and a charge of –1.
II.
They are electrons.
III.
They are less penetrating than α particles.
A.
B.
C.
D.
I and III
II and III
I only
II only
2. An atom of
undergoes radioactive decay by α emission. What is the product nuclide?
3. If 75% of a sample of pure
A. 24.6 yr
A.
B.
C.
D.
decays in 24.6 years, what is the half-life of
?
18.4 yr
12.3 yr
6.15 yr
3.07 yr
Answers and Explanations
1. D—The mass should be 226 – (4 + 4 + 0 + 4) = 214. The atomic number should be 88 – (2 + 2 – 1 + 2)
= 83.
2. B—Mass difference = 234 – 230 = 4, and atomic number difference = 92 – 90 = 2. These correspond to
an α particle.
3. C—Alpha particles are the least penetrating, and gamma rays are the most penetrating.
4. C—Mass difference = 236 – 4(1) – 136 = 96. Atomic number difference = 92 – 4(0) – 53 = 39.
5. A—In nuclear reactions the mass of a β particle is treated as 0, with a charge of –1. Electrons and β
particles are the same thing.
6. B—Mass number = 238 – 4 = 234, and atomic number = 92 – 2 = 90.
7. C—After one half-life, 50% would remain. After another half-life this would be reduced by one-half to
25%. The total amount decayed is 75%. Thus, 24.6 yr must be two half-lives of 12.3 yr each.