AP Chemistry Unit 19 Selected Response Questions:
1) By what process does thorium-230 decay to radium-226?
A) gamma emission
B) alpha emission
C) beta emission
D) electron capture
E) positron emission
Answer: B
2) In balancing the nuclear reaction 238 U
92
__________.
234 E 4 He , the identity of element E is
90
2
A) Pu
B) Np
C) U
D) Pa
E) Th
Answer: E
3) What is the largest number of protons that can exist in a nucleus and still be stable?
A) 206
B) 50
C) 92
D) 83
E) 84
Answer: D
4) The largest number of stable nuclei have an __________ number of protons and an
__________ number of neutrons.
A) even, even
B) odd, odd
C) even, odd
D) odd, even
E) even, equal
Answer: A
5) Bombardment of uranium-235 with a neutron generates tellurium-135, 3 neutrons, and
__________.
A) zirconium-98.
B) krypton-101.
C) krypton-103.
D) strontium-99.
E) zirconium-99.
Answer: A
6) How many neutrons are emitted when a californium-249 nucleus (Z=98) is bombarded
with a carbon-12 nucleus to produce a 257 Rf nucleus ?
104
A) one
B) three
C) two
D) four
E) zero
Answer: D
7) 131I has a half-life of 8.04 days. Assuming you start with a 1.53 mg sample of 131I,
how many mg will remain after 13.0 days?
A) 0.835
B) 0.268
C) 0.422
D) 0.440
E) 0.499
Answer: E
8) What order process is radioactive decay?
A) zeroth
B) first
C) second
D) third
E) fourth
Answer: B
9) On average, __________ neutrons are produced by every fission of a uranium-235
nucleus.
A) 4
B) 3.5
C) 1
D) 2.4
E) 2
Answer: D
10) The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is
the mass defect (in amu) of a 60 Co nucleus? (The mass of a cobalt-60 nucleus is
27
59.9338 amu.)
A) 27.7830
B) 0.5489
C) 0.5405
D) 0.0662
E) 0.4827
Answer: B
Constructed response and performance event questions:
1) What happens in the nucleus of an atom that undergoes positron emission?
Answer: A proton is converted to a neutron and a positron.
2) What happens to the atomic mass number and the atomic number of a radioisotope
when it undergoes alpha emission?
Answer: The mass number drops by 4 and the atomic number decreases by 2.
3) What isotope of what element is produced if krypton-81 undergoes beta decay?
Answer: rubidium-81
4) The first nuclear transmutation resulted in the conversion of nitrogen-14 to
__________.
Answer: oxygen-17
5) The half-life for the beta decay of potassium-40 is 1.3 109 years . What is the rate
constant for this decay?
Answer: t1 2 0.693/ k
1.3 109 years 0.693/ k
k 5.3 10 10 year 1
6) Electrons do not exist in the nucleus, yet beta emission is ejection of electrons from the
nucleus. How does this happen?
Answer: A neutron breaks apart to produce a proton and an electron in the nucleus. The
proton remains in the nucleus and the electron is ejected.
7) List the common particles and their symbols used in descriptions of radioactive decay
and nuclear transformations.
Answer:
8) When an isotope undergoes electron capture, what happens to the captured electron?
Answer: It combines with a proton in the nucleus to form a neutron.
9) The use of radioisotopes in tracing metabolism is possible because __________.
Answer: all isotopes of an element have identical chemical properties
10) The amount of fissionable material necessary to maintain a chain reactions is called
the __________.
Answer: critical mass