Chapter 24

Explain the purpose of control rods in a nuclear reactor.

Why is the fuel of a nuclear reactor enriched?

Explain how it is possible that fission, the splitting of nuclei, and fusion, the combining of nuclei, both release tremendous amounts of energy.

Describe the current limitations of fusion as a power source.

Why does nuclear fusion require so much heat? How is heat contained within a tokamak reactor?

Smoke Detectors Americium-241, a radioisotope used in smoke detectors, is produced by bombarding plutonium-238 with neutrons to produce plutonium-240, which is bombarded with neutrons to produce plutonium-241. The plutonium-241 decays to americium-241. Write the balanced nuclear equations for each reaction.

Exit signs Exit signs are coated with a paint containing phosphors. These phosphors are activated by the radioisotope tritium \(\left(\begin{array}{l}{3} \\\ {1}\end{array} \mathrm{H}\right)\) produced by bombarding lithium-6 with neutrons to produce lithium- \(7 .\) The lithium- 7 then undergoes alpha decay to produce the tritium. Write balanced nuclear equations for both steps.

Control Rods Bombarding uranium-235 with neutrons produces samarium-149, which is used in nuclear reactor control rods. What other element is produced?

The Sun \(_{1}^{1} \mathrm{H}+_{1}^{2} \mathrm{H} \longrightarrow_{2}^{3} \mathrm{He}+\gamma\) is one of the fusion reactions in the Sun. The mass of \(_{1}^{1} \mathrm{H}\) is 1.007825 amu, the mass of \(_{1}^{2} \mathrm{H}\) is \(2.014102 \mathrm{amu},\) and the mass of \(_{2}^{3} \mathrm{He}\) is 3.016029 \(\mathrm{amu}\) a. What is the mass deffect of \(_{2}^{3}\) He? b. What energy is released by the process?

What property of isotopes allows radiotracers to be useful in studying chemical reactions?

Which unit of radiation dose, rem or rad, is most useful for describing the effect of radiation on living tissue?

PET scans In PET scans, the radiotracer emits positrons, which travel a few millimeters before interacting with electrons. How can the original radiotracer be detected?

A worker stands near a machine that uses a cobalt-60 gamma source to sterilize medical equipment. The worker's dose 2.0 \(\mathrm{m}\) from the source is 0.85 \(\mathrm{mrem} / \mathrm{s} \cdot \mathrm{m}^{2}\) What is the worker's dose at a distance of 3.5 \(\mathrm{m}\) ?

Safe Exposure The intensity of a radioactive source is 1.15 mrem/s \(\cdot \mathrm{m}^{2}\) at a distance of 0.50 \(\mathrm{m}\) . What is the minimum distance a person could be from the source to have a maximum exposure of 0.65 \(\mathrm{mrem} / \mathrm{s} \cdot \mathrm{m}^{2} ?\)

Technetium-104 has a half-life of 18.0 min. How much of a 165.0 g sample remains after 90.0 minutes have passed?

A bromine-80 nucleus can decay by gamma emission, positron emission, or electron capture. What is the product nucleus in each case?

Red blood cells A medical researcher is using a chromium- 51 source to study red blood cells. The gamma-emission intensity at a distance of 1.0 \(\mathrm{m}\) is 0.75 mrem \(/ \mathrm{s} \cdot \mathrm{m}^{2}\) At what distance would the intensity drop to 0.15 mrem \(/\) s.m \(^{2} ?\)

The binding energy per nucleon reaches a maximum around what mass number? Explain how this number is related to the fission and fusion processes

You have an alpha source, a beta source, and a gamma source. Design a plan to use a Geiger counter, paper, and foil to determine the identity of each source.

What is the half-life of radon-222 if a sample initially contains 150 mg and only 18.7 mg after 11.4 days?

Apply Chemical treatment is often used to destroy harmful chemicals. For example, bases neutralize acids. Why can’t chemical treatment be applied to destroy the fission products produced in a nuclear reactor?

Compare A biological concern about working around some radioactive materials is the radioactive dust a person might inhale. Compare the effect of alpha radiation outside the body and inside the body.

Interpret Small radioactive sources are often used for laboratory experiments. The radioactive substance is enclosed in a metal container with a small window. A gamma source might be covered with a stainless steel window. What would you expect the window of an alpha source to be like? Why?

Analyze Some radioisotopes used for medical imaging have half-lives as short as several hours. Why is a short half-life beneficial? Why is it a problem?

Infer The production of electricity at nuclear fission reactor facilities is controversial. Think about the benefits and dangers of this technology. Explain your opinion about whether nuclear reactors should be used

Identify each property as chemical or physical. (Chapter 3) a. The element mercury has a high density. b. Solid carbon dioxide sublimes at room temperature. c. Zinc oxidizes when exposed to air. d. Sucrose is a white crystalline solid.

Why does the second period of the periodic table contain eight elements? (Chapter 6)

Draw each molecule and show the locations of hydrogen bonds between the molecules. (Chapter 8\()\) a. two water molecules b. two ammonia molecules c. one water molecule and one ammonia molecule

What process takes place in each situation? (Chapter 12\()\) a. a solid air-freshener cube getting smaller and smaller b. dewdrops forming on leaves in the morning c. steam rising from a hot spring d. a crust of ice forming on top of a pond

If the volume of a sample of chlorine gas is 4.5 L at 0.65 atm and 321 K, what volume will the gas occupy at STP? (Chapter 13)

The temperature of 756 \(\mathrm{g}\) of water in a calorimeter increases from \(23.2^{\circ} \mathrm{C}\) to \(37.6^{\circ} \mathrm{C} .\) How much heat was given off by the reaction in the calorimeter? (Chapter 15\()\)

Explain what a buffer is and why buffers are found in body fluids. (Chapter 18)

Explain how the structure of benzene can be used to explain its unusually high stability compared to other unsaturated cyclic hydrocarbons. (Chapter 21)

Marie Curie and Irene Curie Joliot Research and report on the lives of Marie Curie and her daughter, Irene Curie Joliot. What kind of scientific training did each receive? What was it like to be a female chemist in their time? What discoveries did each make?

Fluorine-18 is used in medical imaging. If a lab has a sample containing 15 g of fluorine-18, how much fluorine-18 will remain in the sample after 8.0 h?