Deck 21: Nuclear Chemistry

Question 1

Uranium-238 ( ) decays to form thorium-234 ( ) with a half-life of 4.5 * 10⁹ years. How many years will it take for 75% of the uranium-238 to decay?

A) 9.0 * 10¹⁰ years
B) 4.5 *10⁹ years
C) 4.5*10¹⁰ years
D) 9.0 * 10⁹ years
E) 3.8 *10⁹ years

Answer 1

9.0 * 10⁹ years

Question 2

The first step in the disintegration of uranium is . What particle is emitted in this reaction?

A) " $\alpha$ " particle
B) neutron
C) proton
D) electron
E) " $\gamma$ " ray

Answer 2

" $\alpha$ " particle

Question 3

Which reactant and product would balance the following nuclear reaction equation? reactant + ¹²C $\rightarrow$ ¹¹B + product

A) reactant = $\beta$ ^-, product = ¹H
B) reactant = $\beta$ ⁺, product = ¹n
C) reactant = $\beta$ ^-, product = ¹n
D) reactant = $\beta$ ⁺, product = $\alpha$
E) reactant = ¹H, product = $\alpha$

Answer 3

reactant = $\beta$ ^-, product = ¹n

Question 4

Tritium, (³H) is used in glowing "EXIT" signs located where there is no electricity for light bulbs. If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 18.5 years?

A) 0.632%
B) 63.2%
C) 35.1%
D) 1.51%
E) 25.0%

Question 5

In 2002, a wooden beam from the Wupatki Indian ruin in Arizona was found to contain 235 mg of carbon-14. A sample of wood of the same mass cut sometime in 2002 contained 264 mg of carbon-14. When was the beam from Wupatki cut if the half-life of carbon-14 is 5715 years?

A) 1974 AD
B) 750 AD
C) 959 AD
D) 1042 AD
E) 926 AD

Question 6

Compare the energy released by the collisions and annihilation of (1) an electron and a positron and (2) a proton and an antiproton.

A) The energy released would be the same.
B) The energy released in (2) would be much greater than that released in (1).
C) The energy released in (1) would be much greater than that released in (2).
D) Energy is consumed in these processes, not released.
E) Energy is not released in these collisions.

Question 7

Which statement is not correct? In hydrogen fusion in our sun, __________

A) a neutron and a proton fuse together to form a deuteron.
B) two protons fuse together to form a deuteron and a positron.
C) a deuteron and a proton fuse to produce a helium-3 nuclide.
D) two helium-3 nuclides fuse to produce a helium-4 nuclide and two protons.
E) more stable nuclides are produced from less stable nuclides.

Question 8

Why are higher temperatures necessary for fusion of helium nuclei than for hydrogen nuclei?

A) Helium is chemically inert.
B) Helium nuclei are heavier than hydrogen nuclei.
C) The positive charges on helium nuclei are greater than those on the hydrogen nuclei.
D) Because E = mc² and helium nuclei are heavier than hydrogen nuclei.
E) The boiling point of helium is higher than that of hydrogen.

Question 9

Which statement is not correct? During primordial nucleosynthesis, __________

A) neutrons and protons fused together to form deuterons.
B) deuterons fused together to form alpha particles.
C) more stable nuclides were formed from less stable nuclides.
D) gamma rays were produced.
E) colliding pairs of electrons annihilated each other.

Question 10

The half-life of a radioactive isotope is 1.0 minute. In an experiment, the number of decay events was monitored in 1-minute intervals over a 5-minute period. What would you predict for the most likely observations if 50 decay events were observed in the first minute? In the second minute, __________ events were observed, and in the last minute, __________ events were observed.

A) 50, 50
B) 25, 3
C) 25, 25
D) 50, 100
E) 25, 13

Question 11

Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland. If a patient drinks a sodium iodide (NaI) solution containing iodine-131 on a Tuesday, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration?

A) 19 days
B) 0.81 day
C) 8.1 days
D) 35 days
E) 4.3 days

Question 12

A half-life is __________

A) the life that a nuclear chemist leads.
B) half of the lifetime of an unstable nucleus.
C) the time for one-half of the unstable nuclei to decay.
D) constantly changing.
E) independent of the rate constant for decay.

Question 13

Extremely high temperatures are required to initiate nuclear fusion, but then energy is released by nuclear fusion. This is analogous to __________

A) boiling a liquid by heating it.
B) melting a solid by heating it.
C) lighting a match to start a fire.
D) two magnets attracting each other.
E) climbing up a hill and then skiing down.

Question 14

Prozac (fluoxetine hydrochloride) is a selective serotonin reuptake inhibitor (SSRI) used to treat depression. Its function in the brain can be studied by using radiolabeled ¹⁸F instead of natural abundance fluorine in its structure. The positron emission is detected by a PET scan. The half-life of ¹⁸F is 109.7 minutes. If radiolabeled Prozac were administered to a patient for a PET scan at 8:00 A.M. on Monday, at what time would its activity reach 10% of the original activity?

A) 9:49 A.M., Monday
B) 9:07 P.M., Friday
C) 10:42 A.M., Tuesday
D) 2:04 P.M., Monday
E) 6:07 P.M., Monday

Question 15

Cobalt-60 is a radioactive isotope of Co that is used for radiation therapy. It is produced originally from iron-58 ( ) according to the step . Which particle did the iron-58 absorb to become iron-59?

A) " $\alpha$ " particle
B) neutron
C) proton
D) electron
E) " $\gamma$ " ray

Question 16

As the charges of identical small nuclei increase, the energy required to initiate nuclear fusion of them __________

A) decreases.
B) increases.
C) stays the same.
D) is proportional to their mass.
E) is inversely proportional to their mass.

Question 17

When a positron and an electron collide, they __________

A) form a neutron.
B) strongly repel one another and recoil.
C) annihilate each other and produce gamma rays.
D) form a proton.
E) form a neutron and emit gamma rays.

Question 18

What other particle is formed in the fusion of two protons to form deuterium?

A) proton
B) neutron
C) electron
D) positron
E) " $\gamma$ " ray

Question 19

Hydrogen fusion always produces __________

A) an increase of mass number.
B) " $\beta$ " particles.
C) a new element.
D) a change in the atomic number.
E) positrons.

Question 20

Phosphorus-32 is a radioactive isotope used as a tracer in the liver. How much phosphorus-32 was originally used if there is only 3.50 mg left in a sample after 288 h? (The half-life of phosphorus-32 is 14.3 days.)

A) 1.96 mg
B) 6.26 mg
C) 4.17 mg
D) 7.00 mg
E) 17.9 mg

Question 21

K-capture is associated with __________

A) conversion of a neutron to a proton.
B) conversion of a proton to a neutron.
C) increase in mass number.
D) decrease in mass number.
E) emission of $\gamma$ rays.

Question 22

Positron emission is associated with __________

A) conversion of a neutron to a proton.
B) conversion of a proton to a neutron.
C) increase in mass number.
D) decrease in mass number.
E) emission of $\gamma$ rays.

Question 23

Strontium-88 is the most abundant stable isotope. Strontium-90 is a particularly hazardous radioactive isotope because, as an alkali earth metal, it will substitute for calcium in bones and teeth. Predict its decay pathway.

A) " $\alpha$ " emission
B) " $\beta$ " emission
C) positron emission
D) " $\gamma$ " emission
E) X-ray emission

Question 24

The isotope "belt of stability" is an area in a plot of __________

A) nuclear binding energy vs. atomic number.
B) isotopic strength vs. isotopic weakness.
C) nuclear mass vs. mass number.
D) neutron number vs. atomic number.
E) mass number vs. atomic number.

Question 25

The natural abundance of uranium-235 is __________

A) a little less than 1%.
B) about 3-5%, depending on the source.
C) close to 100%.
D) 0%, the isotope is made by transmutation.
E) approximately 40%.

Question 26

Nuclear fission produces energy because __________

A) neutrons are produced.
B) the total mass of the products is less than that of the reactants.
C) the total mass of the products is more than that of the reactants.
D) it is a very powerful chemical reaction.
E) photons are produced.

Question 27

Beta emission is associated with __________

A) conversion of a neutron to a proton.
B) conversion of a proton to a neutron.
C) increase in mass number.
D) decrease in mass number.
E) emission of $\gamma$ rays.

Question 28

Electricity is produced from nuclear reactions by __________

A) capturing the electrons that are emitted.
B) accelerating electrons with rapidly moving protons from the nuclear reaction.
C) a process still not understood by scientists.
D) using the energy to make steam to turn turbines.
E) using the energy to accelerate electrons in wires.

Question 29

The peak in nuclear binding energy/nucleon occurs for an isotope of __________

A) helium.
B) iron.
C) uranium.
D) carbon.
E) lead.

Question 30

Light elements with Z < 20 generally have a neutron/proton ratios about equal to __________

A) 0.5.
B) 0.8.
C) 1.0.
D) 1.3.
E) 1.5.

Question 31

Uranium-235 is the fuel in nuclear power plants. When a nucleus of uranium-235 captures a neutron, the nucleus splits into two lighter nuclei and initiates a chain reaction. The chain reaction is driven by the emission of __________

A) protons.
B) neutrons.
C) positrons.
D) " $\beta$ " particles.
E) " $\alpha$ " particles.

Question 32

The heaviest elements will generally have a neutron/proton ratio about equal to __________

A) 0.5.
B) 0.8.
C) 1.0.
D) 1.3.
E) 1.5.

Question 33

The difference between the uranium used in an atomic bomb and that used in a nuclear power plant is that __________

A) there is no difference.
B) the percentage of uranium-238 is much higher in the bomb.
C) the percentage of uranium-235 is much higher in the bomb.
D) the uranium in the bomb is 99.9% pure uranium.
E) the uranium in the bomb is mixed with plutonium.

Question 34

The purpose of control rods in a fission reactor is to __________

A) cool down the reactor fuel.
B) prevent oxygen from reaching the fuel.
C) absorb neutrons generated in the fission process.
D) absorb the electrons emitted in the fission process.
E) enhance the neutron capture process.

Question 35

What repulsive forces must be overcome for any element other than hydrogen to exist?

A) The repulsion between neutrons and other neutrons.
B) The repulsion between protons and other protons.
C) The repulsion between protons and neutrons.
D) The repulsion between positrons and electrons.
E) The repulsion between neutrons and electrons.

Question 36

Rhenium-185 is a stable isotope. Rhenium-188 is a radioisotope for treatment of cancer. What type of emission is likely for this isotope?

A) " $\alpha$ "
B) " $\beta$ "
C) positron
D) " $\gamma$ " ray
E) X-ray

Question 37

The mass of a particular isotope is given by __________

A) the mass number.
B) adding the masses of protons, neutrons, and electrons.
C) measuring it.
D) dividing the mass number by 6.02 *10²³.
E) dividing the molar mass of the element by 6.02 * 10²³.

Question 38

Nuclear fusion produces energy because __________

A) neutrons are produced.
B) the total mass of the products is less than that of the reactants.
C) the total mass of the products is more than that of the reactants.
D) it is a very powerful chemical reaction.
E) photons are produced.

Question 39

Cobalt-59 is a stable isotope. Cobalt-60 is used as a radioactive source approved by the FDA for irradiation of food. This process kills microbes and insects and can delay ripening. What decay pathway is likely for cobalt-60?

A) " $\alpha$ " emission
B) " $\beta$ " emission
C) positron emission
D) " $\gamma$ " emission
E) X-ray emission

Question 40

Tritium (³H) is used in glowing "EXIT" signs conveniently located where there is no electricity for light bulbs. What decay route is likely for tritium?

A) " $\alpha$ " emission
B) " $\beta$ " emission
C) positron emission
D) " $\gamma$ " emission
E) X-ray emission

Question 41

All elements with Z > 83 are __________

A) synthetic.
B) produced by nuclear fission.
C) radioactive.
D) not found in nature.
E) unreactive.

Question 42

Plutonium-238 is an $\alpha$ emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it was once used as a very reliable electrical energy source for cardiac pacemakers. What is the product of the radioactive decay of plutonium-238?

A) thorium-230
B) uranium-234
C) curium-242
D) californium-246
E) plutonium-234

Question 43

In a Geiger counter, which is used to detect radioactivity, a particle produced by radioactive decay __________

A) ionizes an inert gas to produce a pulse of electrical current.
B) heats up an inert gas to produce a temperature pulse.
C) excites a phosphor to produce a pulse of visible light.
D) hits a metal plate to produce a voltage pulse.
E) hits a metal plate, vaporizing atoms, to produce a pressure pulse.

Question 44

Why is a nuclear power plant not in danger of producing a nuclear explosion?

A) Control rods are in place that absorb all the neutrons.
B) The uranium-235 fuel is not pure enough.
C) The uranium-235 fuel is kept cool by a cooling system.
D) The uranium-235 fuel is not able to produce an explosive chain reaction.
E) Nuclear explosions can only occur through fusion, not fission.

Question 45

The heaviest stable nucleus is an isotope of __________

A) platinum.
B) gold.
C) lead.
D) bismuth.
E) xenon.

Question 46

Crews of commercial airlines are exposed to a higher level of background cosmic radiation during flight time than they would receive on the ground. A single round-trip, coast-to-coast flight gives a dose of about 0.012 rems. If a stewardess made 200 such flights in one year, how would her annual dose compare with a normal annual exposure on the ground of 3.6 mSv? (100 rem = 1 Sv)

A) About the same.
B) A bit less than 10 times more.
C) A bit larger than 10 times more.
D) A bit less than 100 times more.
E) A bit larger than 100 times more.

Question 47

The dominant mechanism through which radiation damages biological tissue and living organisms is by __________

A) overheating the tissue.
B) making the tissue radioactive.
C) directly breaking bonds in DNA.
D) directly ionizing biological molecules.
E) ionizing water and producing hydroxy radicals.

Question 48

Radon gas is dangerous __________

A) because it binds to hemoglobin and inhibits the uptake of oxygen.
B) only if it is absorbed inside the body.
C) because it is an alpha emitter.
D) because of both reasons, B and C.
E) for all three reasons above, A, B, and C.

Question 49

Which one of the following statements, A-D, is not correct? If all are correct, respond E. A breeder reactor __________

A) converts naturally abundant uranium-238 into plutonium-239.
B) converts unfissionable uranium-238 into fissionable plutonium-239.
C) produces more fuel than it consumes in producing energy.
D) is considered to be too hazardous for use in the United States.
E) A-D are all correct.

Question 50

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s). An older unit for activity is the curie (1 Ci = 3.70 *10¹⁰/s). What is the activity in Bq of a sample with an activity of 47 µCi of radiation?

A) 7.9 * 10² Bq
B) 7.9 * 10⁸ Bq
C) 1.7 *10¹² Bq
D) 1.7 * 10⁶ Bq
E) 1.3* 10^-16 Bq

Question 51

Which statement, A-D, regarding the activity of a radioactive sample, is not correct? If all are correct, respond E.

A) The activity of a sample is the number of decay events per second.
B) The activity depends on a rate constant for the decay and the amount of the radioisotope in the sample.
C) Radioactive decay follows first-order reaction kinetics.
D) The activity will decrease to half its initial value in a time equal to ln(2)/k, where k is the rate constant.
E) A-D are all correct.

Question 52

In 1913, an element was known to "emanate" from radium-226 by alpha emission and then to decay to polonium-218, also by $\alpha$ emission. What was the unknown element?

A) radon-222
B) lead-214
C) plutonium-238
D) bismuth-214
E) lead-218

Question 53

Which one of the following statements, A-D, is not correct? If all are correct, respond E. A breeder reactor __________

A) converts uranium-238 into plutonium-239.
B) uses plutonium-239 as fuel.
C) produces more fuel than it uses.
D) produces plutonium-239 by beta emission from uranium-239.
E) A-D are all correct.

Question 54

Which type of radiation has the greatest penetration ability?

A) " $\alpha$ "
B) " $\beta$ "
C) " $\gamma$ "
D) neutron
E) " $\beta$ ⁺"

Question 55

Plutonium-238 is an $\alpha$ emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it is used as a very reliable electrical energy source for cardiac pacemakers. It has a half-life of 86 years and an atomic weight of 238.0495 g/mol. One mol is equal to 6.02 * 10²³ atoms. If 100.0 grams of ²³⁸Pu were used in a pacemaker, how many $\alpha$ particles would it produce in 10 years?

A) 6.02 * 10²³
B) 3.01 *10²³
C) 3.01 *10²²
D) 1.96 *10²²
E) 2.33 *10²³

Question 56

Which of the following units is used to quantify the biological effects of radiation?

A) curies
B) rems
C) rads
D) becquerels
E) joules

Question 57

Which type of radiation does the most tissue damage, but only when the emitter is internally ingested?

A) " $\alpha$ "
B) " $\beta$ "
C) " $\gamma$ "
D) neutron
E) " $\beta$ ⁺"

Question 58

Tissue damage caused by radiation is measured in units of Sieverts (Sv) or rems. On average, a person living in the United States is exposed to 3.6 mSv of radiation each year. Space Shuttle astronauts are exposed to about 25 rems of cosmic radiation during a mission. Roughly how does this quantity compare with the annual dose the astronaut would have received on the ground in the United States? (1 Sv = 100 rems)

A) About the same.
B) About 10 time more.
C) A bit less than 100 times more.
D) A bit larger than 100 times more.
E) About 1000 times more.

Question 59

Which of the following units is used to quantify the biological effects of radiation?

A) curies
B) sieverts
C) rads
D) becquerels
E) joules

Question 60

The most naturally abundant nuclides are those that __________

A) have an odd number of protons and an odd number of neutrons.
B) have an even number of protons and an even number of neutrons.
C) have noble gas configurations of electrons.
D) can be produced by fission reactions.
E) can be produced by fusion reactions.

Question 61

A person's body generates about 0.2 µCi of radioactivity! Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 * 10¹⁰ Bq and 1 Bq = 1 decay/s)

A) 2 * 10⁶ decays/s
B) 9 * 10¹⁶ decays/s
C) 70 decays/s
D) 2 *10⁷ decays/s
E) 7 * 10³ decays/s

Question 62

If a nitrogen-14 nuclide captures an alpha particle, a proton is produced along with __________

A) neutrons.
B) boron-10.
C) oxygen-17.
D) fluorine-18.
E) carbon-17.

Question 63

Cardiac pacemakers once used plutonium-238 as a power source. Plutonium-238 decays by the emission of gamma rays and alpha particles. This emission is not particularly harmful because __________.

A) gamma rays are not absorbed very strongly by biological tissue, and alpha particles do not penetrate beyond the container.
B) gamma rays and alpha particles are the least dangerous form of radiation.
C) gamma rays and alpha particles do not penetrate beyond the container.
D) gamma rays are absorbed by the container, and alpha particles do not affect biological tissue.

Question 64

Radon-220 decays to polonium-216. What particle is emitted?

A) beta
B) positron
C) neutron
D) alpha
E) gamma

Question 65

Low-level nuclear waste from medical facilities generally requires only short-term storage before disposal because __________

A) the concentrations of radioactive isotopes used in medicine are very low.
B) the radioactive isotopes are degraded by the medical procedures.
C) the radioactive isotopes used in medicine have short half-lives.
D) the radioactive isotopes used in medicine are selected because they are naturally safe.
E) there is little government regulation regarding the disposal of medical waste.

Question 66

Which of the following nuclides are most likely to be unstable because they have too many neutrons?
(I) carbon-14
(II) sodium-24
(III) silicon-26
(IV) aluminum-27
(V) phosphorous-31

A) only I
B) I and II
C) II and III
D) III, IV, and V
E) all of these

Question 67

Strontium-90 is most likely to decay by __________

A) gamma emission.
B) beta emission.
C) positron emission.
D) alpha emission.
E) electron capture.

Question 68

The activity of a sample of gas obtained from a basement containing radon-222 was found to be 8 pCi/L. This isotope has a half-life of 3.8 days. If no additional radon-222 entered the basement, how long would it take for the activity to decline to 1 pCi/L?

A) about 4 days
B) a bit more than 10 days
C) about 1 day
D) a bit less than 10 days
E) about 20 days

Question 69

Which isotope is produced when ²¹⁶Po decays by emitting an alpha particle followed by 2 beta particles?

A)"²¹⁰Po"
B)"²¹²Po"
C)"²¹⁴Po"
D)"²¹⁸Po"
E)"²²⁰Po"

Question 70

Cobalt-56 decays by emitting a positron. What is the product?

A) cobalt-55
B) cobalt-56
C) nickel-56
D) iron-56
E) iron-55

Question 71

Radon-222 has a half-life of 3.8 days. A sample from a basement in Colorado was analyzed 5.0 days after it was collected and found to have an activity of 0.17 Bq. What was the original activity of this sample?

A) 0.22 Bq
B) 0.32 Bq
C) 0.42 Bq
D) 0.62 Bq
E) 0.52 Bq

Question 72

Among other problems with smoking, there is a danger from radiation, according to the following report! "Tobacco plants are grown in soils with high phosphate fertilizers that are naturally contaminated with the alpha-particle emitting radionuclide polonium-210. In one year, the average smoker will irradiate the bronchial epithelium with 8 to 9 rem, the equivalent dose of radiation from 250 to 300 chest X-ray films per year" (Pediatrics, September 1993, p. 464). How does this annual dose from tobacco compare to an average annual dose of 3.6 mSv that a nonsmoker receives from background radiation? (1 Sv = 100 rem)

A) about 250 times more
B) about 25 times more
C) about 3 times more
D) about 1/4 as much
E) about 1/3 as much

Question 73

Which one of the following statements is not correct?

A) Oxygen-15 is unstable because it has too few neutrons.
B) Nucleons are held together in a nuclide by the electromagnetic force.
C) All nuclides with Z > 83 decay into more stable nuclides with smaller Z values.
D) As the atomic number increases, the ratio of neutrons to protons in a nuclide increases.
E) Generally the number of neutrons in a nuclide equals the number of protons, or nearly so, when the atomic number is small, i.e., Z < 18.

Question 74

Cobalt-60 decays to nickel-60. What particle is emitted?

A) proton
B) neutron
C) electron
D) positron
E) alpha

Question 75

Common activity levels of radon-222 are in the range of 1 picocurie/liter (pCi/L) at room temperature and pressure. How many atoms of radon decay each minute in a 1 L sample of gas with radiation at this level? Recall that 1 Bq = 1 decay/s and 1 Ci = 3.7 * 10¹⁰ Bq.

A) 6 * 10^-4
B) 6*10⁸
C) 2 * 10¹²
D) 2
E) 4* 10^-2

Question 76

Small traces of radioactive substances, mainly from the food we eat, are present in the human body. The most abundant radioisotope in the body is potassium-40. A person weighing 70 kg contains about 150 g of potassium, and about 0.01% of this amount is potassium-40. The half-life of potassium-40 is 1.25 x10⁹ years. Estimate the rate at which radiation is produced by the decay of potassium-40 in the body.

A) 4,000 decays/s
B) 40,000 decays/s
C) 400,000 decays/s
D) 400 decays/s
E) 4 decays/s

Question 77

Which one of the following statements is not correct?

A) Carbon-10 is unstable because it has too few neutrons.
B) All nuclides with Z > 83 decay into nuclides with smaller Z values.
C) Generally, the number of neutrons in a nuclide is equal to or less than the atomic number.
D) As the atomic number increases, the ratio of neutrons to protons in a nuclide increases.
E) It is very unusual to find a nuclide with an odd number of protons and an odd number of neutrons.

Question 78

Uranium-238 decays to lead-206 through a series of nuclear reactions. Only $\alpha$ particles and $\beta$ particles are emitted. How many $\alpha$ particles are emitted?

A) 2
B) 4
C) 6
D) 8
E) 10

Question 79

Nitrogen-13 decays by positron emission to produce __________

A) carbon-13.
B) oxygen-17.
C) boron-11.
D) carbon-14.
E) boron-13.

Question 80

In the initial sequence of thorium-232 decay, an alpha particle is emitted followed by a beta particle. What is the product of these two decay steps?

A) radium-228
B) actinium-228
C) thorium-228
D) francium-228
E) The correct answer differs from these possibilities.