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Nuclear Chemistry
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 01 Print E-mail
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Practice Questions
1. Which reaction illustrates fusion?

A)    13Al27 + 2He4 -> 15P30 + 0n1

B)    7N14 + 2He4 -> 1H1 + 8O17

C)    1H2 + 1H2 -> 2He4

D)    0n1 + 13Al27 - > 11Na24 + 2He4

Correct Answer: Option C - 1H2 + 1H2 -> 2He4

Fusion is the process of joining two light nuclei to form a heavier one. High pressure and high temperatures are used to make this happen. Tremendous energy is released when the fusion takes place. Only answer C shows two light elements combining.

Incorrect Options

A, B, and D are all examples of artificial transmutation or bombardment of an element by a neutron or alpha particle.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 02 Print E-mail
Practice Questions
2. Which nuclear emission has the greatest penetrating power?

A)    Gamma radiation

B)    Alpha particle

C)    Beta particle

D)    Positron

Correct Answer: Option A - Gamma radiation

Gamma rays are electromagnetic radiation of high energy. They are produced by sub-atomic particle interactions, such as electron-positron annihilation, neutral pion decay, radioactive decay, fusion, fission or inverse Compton scattering in astrophysical processes. Gamma rays typically have frequencies above 1019 Hz and therefore energies above 100 keV and wavelength less than 10 picometers, often smaller than an atom.

Gamma rays compete with neutrons as the most dangerous form of ionizing radiation emitted by something such as a nuclear explosion because they are highly penetrating, highly energetic ionizing radiation. Gamma rays have the shortest wavelength of all waves in the electromagnetic spectrum, and therefore have the greatest ability to penetrate through any gap, even a subatomic one, in what might otherwise be an effective shield.

Incorrect Options

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of 1/2, and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two or more gamma ray photons.

Alpha particles (denoted by the first letter in the Greek alphabet, a) consist of two protons and two neutrons bound together into a particle identical to a helium nucleus; hence, it can be written as He2+ or 42He2+. They have a net spin of zero, and normally a total energy of about 5 MeV. They are a highly ionizing form of particle radiation, and have low penetration.

Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay. They are designated by the Greek letter beta (ß).

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 03 Print E-mail
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Practice Questions
3. Which nuclear equation represents a natural transmutation?

A)    4Be9 + 1H1 3Li6+ 2He4

B)    13Al27 + 2He4 15P30+ 0n1

C)    7N14 + 2He4 8O17 + 1H1

D)    92U235 90Th231 + 2He4

Correct Answer: Option D - 92U235 90Th231 + 2He4

Nuclear transmutation is the conversion of one chemical element or isotope into another, which occurs through nuclear reactions. Natural transmutation occurs when radioactive elements spontaneously decay over a long period of time and transform into other more stable elements. Artificial transmutation occurs in machinery that has enough energy to cause changes in the nuclear structure of the elements.

Options A, B and C are examples of artificial transmutation, where the decay process is induced by an external agent. Hence, they are incorrect.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 04 Print E-mail
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4. A nuclear fission reaction and a nuclear fusion reaction are similar because both reactions:

A)    Form heavy nuclides from light nuclides

B)    Release a large amount of energy

C)    Form light nuclides from heavy nuclides

D)    Absorb a large amount of energy

Correct Answer: Option B - Release a large amount of energy

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei, which may eventually produce photons (in the form of gamma rays). Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place).

Nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy, which allows matter to enter a plasma state. The fusion of two nuclei with lower mass than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy while the fusion of nuclei heavier than iron absorbs energy.

Options A and C are incorrect since the opposite is true for both fission and fusion reactions.

Option D is incorrect since, both fusion and fission reactions release large amount of energy.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 05 Print E-mail
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5. To make nuclear fission more efficient, which device is used in a nuclear reactor to slow the speed of neutrons?

A)    Moderator

B)    External shield

C)    Internal shield

D)    Control rod

Correct Answer: Option A - Moderator

Neutrons can be quickly slowed down by colliding with particles such as graphite, heavy water (deuterium oxide), and water. These substances keep the reaction from getting out of control much like a moderator keeps both sides from getting into an argument or fight.

Thermal neutrons (that is, slow neutrons) have the highest probability of producing fission of U-235 but the neutrons emitted in the process of fission have high speeds (they are not thermal). It is an oversimplification to say that the chain reaction might maintain itself if more neutrons were created by fission than were absorbed, because the probability both of fission capture and of non-fission capture depends on the speed of the neutrons. Unfortunately, the speed at which non-fission capture is most probable is intermediate between the average speed of neutrons emitted in the fission process and the speed at which fission capture is most probable. The process of slowing down or moderation is simply one of elastic collisions between high speed particles and particles practically at rest. The more nearly identical the masses of neutron and struck particle, the greater the loss of kinetic energy by the neutron.

Therefore light elements are most effective as neutron moderators. It is possible to mix uranium with a moderator in such a way that the high speed fission neutrons, after being ejected from uranium and before re-encountering uranium nuclei, would have their speeds reduced below the speeds for which non-fission capture is highly probable. The characteristics of a good moderator are that it should be of low atomic weight and that it should have little or no tendency to absorb neutrons. Lithium and boron are excluded on the latter count. Helium is difficult to use because it is a gas and forms no stable compounds. The choice of moderator therefore lay (and still may lie) among hydrogen, deuterium, beryllium, and carbon.

Hence, options B, C and D are incorrect.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 06 Print E-mail
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Practice Questions
6. Particle accelerator can increase the kinetic energy of:

A)    A gamma ray and a beta particle

B)    An alpha particle and a neutron

C)    An alpha particle and a beta particle

D)    Neutron and a gamma ray

Correct Answer: Option C - An alpha particle and a beta particle

A particle accelerator (or atom smasher) is a device that uses electric fields to propel electrically-charged particles to high speeds and to contain them in well-defined beams.

Only charged particles can have their kinetic energy increased in a particle accelerator. (Electric and magnetic fields are used to speed up the particles and these fields have no effect on uncharged particles).

Incorrect Options

Gamma rays are pure energy so you can eliminate answers A and D.

Neutrons have no charge so only alpha particles and beta particles will be affected.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 07 Print E-mail
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Practice Questions
7. Which radioisotope is used in medicine to treat thyroid disorders?

A)    Cobalt-60

B)    Iodine-131

C)    Phosphorus-32

D)    Uranium-238

Correct Answer: Option B - Iodine-131

The thyroid is one of the largest endocrine glands in the body. This gland is found in the neck inferior to (below) the thyroid cartilage (also known as the Adam's apple in men) and at approximately the same level as the cricoid cartilage. The thyroid controls how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones. The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Iodine and tyrosine are used to form both T3 and T4. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.

In humans, children born with thyroid hormone deficiency will have physical growth and development problems, and brain development can also be severely impaired, in the condition referred to as cretinism. Newborn children in many developed countries are now routinely tested for thyroid hormone deficiency as part of newborn screening by analysis of a drop of blood. Children with thyroid hormone deficiency are treated by supplementation with synthetic thyroxine, which enables them to grow and develop normally.

Because of the thyroid's selective uptake and concentration of what is a fairly rare element, it is sensitive to the effects of various radioactive isotopes of iodine produced by nuclear fission. In the event of large accidental releases of such material into the environment, the uptake of radioactive iodine isotopes by the thyroid can, in theory, be blocked by saturating the uptake mechanism with a large surplus of non-radioactive iodine, taken in the form of potassium iodide tablets.

Cobalt-60 is used in treating cancer.

Phosphorus-32 is used as a radioactive tracer in biochemical laboratories.

Uranium-238 is used as a fuel in nuclear reactors.

Hence, options A, C and D are incorrect.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 08 Print E-mail
Practice Questions
8. The energy released by a nuclear reaction results primarily from the

A)    Conversion of mass into energy

B)    Conversion of energy into mass

C)    Breaking of bonds between atoms

D)    Formation of bonds between atoms

Correct Answer: Option A - Conversion of mass into energy

Nuclear energy is released by the splitting (fission) or merging together (fusion) of the nuclei of atom(s). The conversion of nuclear mass to energy is consistent with the mass-energy equivalence formula

E = m.c2

in which E = energy release, m = mass defect, and c = the speed of light in a vacuum (a physical constant).

Hence, options B, C and D are incorrect.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 09 Print E-mail
Practice Questions
9. The nucleus of a radium-226 atom is unstable, which causes the nucleus to spontaneously

A)    Absorb electrons

B)    Decay

C)    Absorb protons

D)    Oxidize

Correct Answer: Option B - Decay

An unstable nucleus is one that undergoes some internal change spontaneously. In this change, the nucleus gives off a subatomic particle, or a burst of energy, or both. As an example, an isotope of carbon, carbon-14, has a nucleus consisting of six protons and eight (rather than six) neutrons. A nucleus that gives off a particle or energy is said to undergo radioactive decay, or just decay.

The forms of radiation most commonly emitted by a radioactive nucleus are called alpha particles, beta particles, and gamma rays. An alpha particle is the nucleus of a helium atom. It consists of two protons and two neutrons. Consider the case of a radium-226 atom. The nucleus of a radium-226 atom consists of 88 protons and 138 neutrons. If that nucleus gives off an alpha particle, it must lose the two protons and two neutrons of which the alpha particle is made. After emission of the alpha particle, the remaining nucleus contains only 86 protons (88 - 2) and 136 neutrons (138 - 2). This nucleus is the nucleus of a radon atom, not a radium atom. By emitting an alpha particle, the radium-226 atom has changed into an atom of radon.

A radioactive element does not absorb protons or electrons or oxidize. Hence, options A, C and D are incorrect.

 
NYS Chemistry Regents Review Practice - Nuclear Chemistry - Question 10 Print E-mail
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10. A serious risk factor associated with the operation of a nuclear power plant is the production of

A)    Greenhouse gases

B)    Acid rain

C)    Helium gas

D)    Radioisotopes with long half-lives

Correct Answer: Option D - Radioisotopes with long half-lives

Decay at a fixed rate is characteristic of an isotope. The rate of decay is a fixed rate called a half-life. The half-life of a radioisotope describes how long it takes for half of the atoms in a given mass to decay. Some isotopes decay very rapidly and, therefore, have a high specific activity. Others decay at a much slower rate. The half-life of a radioisotope is the time required for half the atoms in a given sample to undergo radioactive, or nuclear, decay.

Incorrect Options

Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. Common greenhouse gases in the Earth's atmosphere include water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

Helium is the chemical element with atomic number 2, and is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.

Acid rain is rain or any other form of precipitation that is unusually acidic. It has harmful effects on plants, aquatic animals, and infrastructure. Acid rain is mostly caused by human emissions of sulfur and nitrogen compounds which react in the atmosphere to produce acids. In recent years, many governments have introduced laws to reduce these emissions

 
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