Question 1

Which of the following nuclear equations correctly represents the alpha decay of uranium-238?

Accepted Answer

$$^{238}_{92}\mathrm{U} \$$rightarrow ^{234}$$_{90}\mathrm{Th} $$+ ^{4}$$_{2}\mathrm{He}$$

Question 2

A nuclide with a neutron-to-proton ratio significantly above the belt of stability is most likely to undergo which type of radioactive decay?

Accepted Answer

Beta emission

Question 3

Which of the following statements about gamma radiation is CORRECT?

Accepted Answer

Gamma radiation changes neither the atomic number nor the mass number.

Question 4

Which isotope is most likely to be stable based on the concept of 'magic numbers'?

Accepted Answer

$$^{50}_{20}\mathrm{Ca}$$

Question 5

A sample of $$^{14}\mathrm{C}$$ has decayed to 25% of its original amount. Approximately how many years have passed? (Half-life of $$^{14}\mathrm{C} is 5700 $$years.)

Accepted Answer

11,400 years

Question 6

Which of the following best explains why all nuclei with atomic number $$Z \geq 84$$ are radioactive?

Accepted Answer

They have too many protons for the nuclear force to overcome electrostatic repulsion.

Question 7

Which of the following nuclear reactions represents electron capture?

Accepted Answer

$$^{201}_{80}\mathrm{Hg} $$+ ^{0}$$_{-1}\mathrm{e} \$$rightarrow ^{201}$$_{79}\mathrm{Au}$$

Question 8

Which of the following is a correct statement about the half-life of a radioactive isotope?

Accepted Answer

The half-life is the time required for half of the radioactive nuclei in a sample to decay.

Question 9

Which of the following best describes the process of radiocarbon dating?

Accepted Answer

Measuring the ratio of $$^{14}\mathrm{C} to$$ $$^{12}\mathrm{C} in a $$sample and comparing it to the atmospheric ratio.

Question 10

A radioactive isotope decays with a first-order rate constant $$k = 0.023 \ \mathrm{yr}^{-1}. $$What is its half-life?

Accepted Answer

$$t_{1/2} = \frac{0.693}{0.023} = 30.13 \ \mathrm{yr}$$

Question 11

Which of the following isotopes is most likely to be stable based on the even-odd rule?

Accepted Answer

$$^{58}_{28}\mathrm{Ni} ($$even protons, even neutrons)

Question 12

Which of the following particles is emitted during the beta decay of $$^{14}_{6}\mathrm{C}$$?

Accepted Answer

Beta particle ($$^{0}_{-1}\mathrm{e})$$

Question 13

A sample contains 80 g of a radioactive isotope with a half-life of 10 years. How much of the isotope will remain after 30 years?

Accepted Answer

10 g

Question 14

Which of the following best describes the change in atomic number and mass number during positron emission?

Accepted Answer

Atomic number decreases by 1; mass number unchanged

Question 15

Which of the following is a correct nuclear equation for the beta decay of $$^{210}_{82}\mathrm{Pb}$$?

Accepted Answer

$$^{210}_{82}\mathrm{Pb} \$$rightarrow ^{210}$$_{83}\mathrm{Bi} $$+ ^{0}$$_{-1}\mathrm{e}$$

Question 16

Which of the following best explains why radiocarbon dating is not useful for dating rocks that are millions of years old?

Accepted Answer

The half-life of $$^{14}\mathrm{C} is $$too short, so all $$^{14}\mathrm{C}$$ would have decayed.

Question 17

Which of the following is a real-world application of nuclear chemistry?

Accepted Answer

Using $$^{131}\mathrm{I} to $$treat thyroid cancer

Question 18

If a nucleus with 70 protons is most stable when it has about 96 neutrons, what is the neutron-to-proton ratio?

Accepted Answer

$$\frac{96}{70} = 1.37$$

Nuclear Chemistry: Radioactivity, Nuclear Equations, and Applications

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