chemistry unit 11

On average, how many times would a U.S. resident have to fly across the Atlantic to match the radiation exposure from one year of natural background radiation?

120 -From the chart, the average annual exposure from natural background radiation is 310REM. The exposure from a single transatlantic flight is 2.5REM. Therefore, the background exposure is about 310REM/2.5REM=124 times greater than a transatlantic flight. The answer should have two significant figures, so round to 120.

A sample of iodine-131 was used in a procedure 40 days ago and now 5.00 mCi remain. What was the size of the original sample? (Iodine-131 has a half life of 8 days.) Use three significant figures in your answer.

159.57

A sample of technetium-99 was used in a procedure to image the heart muscle of a patient 36 hours ago and now 2.50 mCi remain. What was the size of the original sample? (Technetium-99 has a half life of 6 hours.) Select the correct answer below: 20.0 mCi 40.0 mCi 80.0 mCi 160. mCi

160. mCi First, figure out how many half-lives have elapsed. 36 hours×1 half-life 6 hours=6 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 2.50 mCi→5.00 mCi→10.0 mCi→20.0 mCi→40.0 mCi→80.0 mCi→160 mCiThe original amount contained 160. mCi.

If an element has a half-life of 20 million years and 6.25% remains in the sample, how old is the sample? Select the correct answer below: -20 million years old -80 million years old -10 million years old -160 million years old

80 million years old

Which description best fits the definition of nuclear reaction? Select the correct answer below: -A nuclear reaction is the combination of very light nuclei into -heavier nuclei, accompanied by the conversion of mass into large amounts of energy. -A nuclear reaction is the separation of a chemical compound into elements or simpler compounds. -A nuclear reaction is the bombardment of one type of nuclei with other nuclei or neutrons. -A nuclear reaction is a change to a nucleus, resulting in changes in its atomic number, mass number, or energy state.

A nuclear reaction is a change to a nucleus, resulting in changes in its atomic number, mass number, or energy state.

Which of the following best describes the term nucleon? Select the correct answer below: -A nucleon is the unstable nuclide that decays spontaneously into another nuclide. -A nucleon is a particle that resides in the nucleus of an atom. -A nucleon is another word for a neutron. -A nucleon is another word for a proton.

A nucleon is a particle that resides in the nucleus of an atom.

Conduct Calculations Involving Half-Life of a Radioisotope The Half-Life of a Reaction The half-life of a reaction, (t1/2), is the time required for one-half of a given amount of reactant to be consumed. In each succeeding half-life, half of the remaining concentration of the reactant is consumed. Using the decomposition of hydrogen peroxide (Figure 1) as an example, we find that: 1st Half-Life: During the first half-life (from 0.00hours to 6.00hours), the concentration of H2O2 decreases from 1.000M to 0.500M. 2nd Half-Life: During the second half-life (from 6.00hours to 12.00hours), it decreases from 0.500M to 0.250M. 3rd Half-Life: During the third half-life, it decreases from 0.250M to 0.125M. The concentration of H2O2 decreases by half during each successive period of 6.00hours. The decomposition of hydrogen peroxide is a first-order reaction, and the half-life of a first-order reaction is independent of the initial concentration of the reactant. This means that it will always take 6.00hours for half of a given amount of hydrogen peroxide to be consumed.

A table with five columns is shown. The first column is labeled, "Time, h." Beneath it the numbers 0.00, 6.00, 12.00, 18.00, and 24.00 are listed. The second column is labeled, "[ H subscript 2 O subscript 2 ], mol / L." Below, the numbers 1.000, 0.500, 0.250, 0.125, and 0.0625 are double spaced. To the right, a third column is labeled, "capital delta [ H subscript 2 O subscript 2 ], mol / L." Below, the numbers negative 0.500, negative 0.250, negative 0.125, and negative 0.062 are listed such that they are double spaced and offset, beginning one line below the first number listed in the column labeled, "[ H subscript 2 O subscript 2 ], mol / L." The first two numbers in the second column have line segments extending from their right side to the left side of the first number in the third row. The second and third numbers in the second column have line segments extending from their right side to the left side of the second number in the third row. The third and fourth numbers in the second column have line segments extending from their right side to the left side of the third number in the third row. The fourth and fifth numbers in the second column have line segments extending from their right side to the left side of the fourth number in the third row. The fourth column in labeled, "capital delta t, h." Below the title, the value 6.00 is listed four times, each single-spaced. The fifth and final column is labeled "Rate of Decomposition, mol / L / h." Below, the following values are listed single-spaced: negative 0.0833, negative 0.0417, negative 0.0208, and negative 0.0103. Figure 1. The rate of decomposition of H2O2 in an aqueous solution decreases as the concentration of H2O2 decreases. Another example of a first-order process is radioactive decay. The spontaneous change of an unstable atomic nucleus into a more stable form is called radioactive decay. We will not concern ourselves here with the details of such nuclear reactions, but we want to apply our understanding of half-life to understand how fast such reactions happen. Each radioactive nucleus has a characteristic, constant half-life (t1/2), the time required for half of the atoms in a sample to decay. An isotope's half-life allows us to determine how long a sample of a useful isotope will be available, and how long a sample of an undesirable or dangerous isotope must be stored before it decays to a low-enough radiation level that is no longer a problem. For example, cobalt-60, an isotope that emits gamma rays used to treat cancer, has a half-life of 5.27years (see Figure 2 below). In a given cobalt-60 source, since half of the 6027Co nuclei decay every 5.27years, both the amount of material and the intensity of the radiation emitted is cut in half every 5.27years. This is as expected for a process following first-order kinetics. Thus, a cobalt-60 source that is used for cancer treatment must be replaced regularly to continue to be effective. For cobalt-60, which has a half-life of 5.27 years, 50% remains after 5.27 years (one half-life), 25% remains after 10.54 years (two half-lives), 12.5% remains after 15.81 years (three half-lives), and so on. Figure 2. For cobalt-60, which has a half-life of 5.27years, 50% remains after 5.27years (one half-life), 25% remains after 10.54years (two half-lives), 12.5% remains after 15.81years (three half-lives), and so on.

A sample of iodine-131 was used in a procedure 40 days ago and now 1.50 mCi remain. What was the size of the original sample? (Iodine-131 has a half life of 8 days.) Use three significant figures in your answer. Provide your answer below:

Correct answers:48.0mCi>48.0 mCi​> First, figure out how many half-lives have elapsed. 40 days×1 half-life8 days=5 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 1.50 mCi→3.00 mcg→6.00 mCi→12.0 mCi→24.0 mCi→48.0 mCiThe original amount contained 48.0 mCi.

Radioactive tracers are used in _______________. Select the correct answer below: -medical applications -analyzing the geological formation around oil wells -tracking engine wear -all of the above

all of the above

Radioactive tracers are used in _______________. medical applications analyzing the geological formation around oil wells tracking engine wear all of the above

all of the above

Which of the following is included in a nuclide symbol? chemical symbol for the element atomic number mass number all of the above

all of the above

Positron emission is most likely to occur if a nucleus:

has a neutron to proton ratio that is too small -If there are too many protons in the nucleus, positron emission occurs. This signifies the conversion of a proton into a neutron, which corrects the proton : neutron ratio.

at radioactive isotope becomes concentrated in healthy heart tissue? Select the correct answer below: -sodium-24 -potassium-39 -thallium-201 -iodine-131

thallium-201

Iodine-123 is a radioisotope that is also used in medical imaging. It is more expensive than iodine-131, but it also emits primarily γ-radiation, while iodine-131 emits most of its energy as β-radiation. The decay of iodine-123 involves electron capture, where a proton in the nucleus is transformed into a neutron. What isotope is produced by this process for iodine-123? Give both the mass number and atomic number by using the nuclide format button to enter your answer in the format AZX.

Iodine-123 has 53 protons and 70 neutrons. Converting one proton to a neutron gives 52 protons and 71 neutrons. The resulting isotope is 123/52Te. I53123+n10⟶I53124⟶Te52123+β−10+200γ

Which statements below that is true of β decay?

It is most likely to occur when the neutron:proton (n:p) ratio of the nuclide is too large. -If there are too many neutrons in the nucleus, β emission occurs. The loss of an electron from the nucleus signifies the conversion of a neutron into a proton, which decreases the neutron:proton (n:p) ratio and increases the atomic number by 1. The mass number remains the same. Gamma emission, not beta emission, occurs when a nucleus is in an excited state.

Which of the following radioactive isotopes has the longest half-life? Select the correct answer below: -Uranium-238 -Carbon-14 -Potassium-40 -Rubidium-87

Rubidium-87 -Carbon-14 has a half life of approximately 5800 years, uranium-238 has a half-life of 4.5 billion years, potassium-40 has a half-life of 1.25 billion years, and rubidium-87 has a half life of 48.8 billion years. Therefore, rubidium-87 has the longest half-life.

In a nuclear reaction, what is rearranged?

Subatomic particles

A worker at a nuclear facility was accidently exposed to radiation and absorbed a total of f 0.20 J of alpha particle radiation, which has an RBE of 10. If his mass is 80.0 kg, what was the radiation dose in rem? Round your answer to two significant figures (round to the nearest tenth).

The relative biological effectiveness (RBE) for radiation of type R on a tissue: RBE = DX / DR where DX is a reference absorbed dose of radiation of a standard type X, and DR is the absorbed dose of radiation of type R that causes the same amount of biological damage. DR = DX / RBE = (0.20 J / 80.0 kg) / 10 = 0.00025 J/kg = 0.00025 J/kg [10000 rem / (1 J/kg)] = 2.5 rem -First calculate the dosage in rad, which is defined by the conversion 1 rad=0.01 Jkg. To do so, divide the energy by the worker's mass and multiply by the conversion factor 1 rad0.01 Jkg. 0.20 J80.0 kg×1 rad0.01 Jkg=0.25 rad To convert the dose in rad to an effective dose in REM, multiply by the RBE of 10. 0.25 rad×10=2.5 rem

Use the following table of radiation health effects to answer the question below. Exposure (rem)5 to 105055707590100400100010001000200020002000Health Effectchanges in blood chemistrynauseafatiguevomitinghair lossdiarrheahemorrhagepossible deathdestruction of intestinal lininginternal bleedingdeathdamage to central nervous systemloss of consciousnessdeathTime to OnsetWithout Treatment—hours——2 to 3 weeks——within 2 months——1 to 2 weeks—minuteshours to days What is the lethal dose (mrem) with a time of onset of a few hours? That's not right. $$50 mrem Answer Explanation Correct answers:$2000\ \text{mrem}$2000 mrem​ From the table, death may occur with doses as low as 400 mrem, but the onset times are longer. For an onset time of hours, the dosage must be closer to 2000 mrem.

2000 rem

Which characteristics of a radioisotope make it good for medical imaging applications (so it can be used as a radioactive tracer)? Select all that apply. Select all that apply: -a very short half-life (less than one second) -a moderate half-life (a few hours to a few days) -a very long half-life (many years) -emits primarily α-radiation -emits primarily γ-radiation -emits primarily β-radiation

Correct answer: -a moderate half-life (a few hours to a few days) -emits primarily γ-radiation The ideal radioisotope for imaging emits only pure γ-radiation because that is easily detected and also not quickly absorbed by the body. It should also have a long enough half-life to be easy to administer, but still be short so that it provides a strong enough signal for the imager.

The half-life of a first-order reaction is 30.0 seconds. What is the rate constant k for the reaction? Select the correct answer below: -0.0100s−1 -9.03s−1 -20.8s−1 -0.0231s−1

Correct answer: 0.0231s−1 For a first-order reaction: t1/2=ln 2k To solve for k, the equation can be rearranged tok=ln 2t1/2t1/2=30.0 s is then substituted into this equation to solve for k.k=ln 2t1/2=ln 230.0 s=0.0231 s−1

A sample of copper-64 was used in a procedure to study copper metabolism 52 hours ago and now 3.50 mCi remain. What was the size of the original sample? (Copper-64 has a half life of 13 hours.) Select the correct answer below: -14.0 mCi -28.0 mCi -56.0 mCi -112 mCi

Correct answer: 56.0 mCi First, figure out how many half-lives have elapsed. 52 hours×1 half-life13 hours=4 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 3.50 mCi→7.00 mCi→14.0 mCi→28.0 mCi→56.0 mCiThe original amount contained 56.0 mCi.

List the radioactive tracers used in medicine. Select the correct answer below: -technetium-99 -thallium-201 -iodine-131 -All of the above. -None of the above.

Correct answer: All of the above. Four typical examples of radioactive tracers used in medicine are technetium-99 (9943Tc), thallium-201(20181Tl), iodine-131(13153I), and sodium-24(2411Na).

Which of the following is used to treat thyroid conditions? Select the correct answer below: Iodine-131 -Tc-99 and Tl-201 -Tc-99 -Tl-201 -None of the above.

Correct answer: Iodine-131 Iodine-131 concentrates in the thyroid gland, so it can be used to treat thyroid conditions such as Grave's disease.

How is cobalt-60 obtained for use in radiation treatment? Select the correct answer below: -It is prepared by irradiating cobalt-59 with neutrons. -It is obtained from the decay of uranium-235. -It is a naturally occurring isotope. -It is prepared by irradiating nickel-60 with neutrons.

Correct answer: It is prepared by irradiating cobalt-59 with neutrons. Cobalt-60 is a synthetic radioisotope produced by the neutron activation of cobalt-59.

Since radioactive isotopes have the same chemical properties as stable isotopes, select the best medical use for the isotope calcium-47? Select the correct answer below: -To study heart tissue -To image the brain -To investigate bone metabolism problems -To image gastrointestinal issues

Correct answer: To investigate bone metabolism problems Calcium-47 is used to in the diagnosis of bone and calcium metabolism disorders. It has a half life of 4.54 days.

What is introduced into the body for brachytherapy? Select the correct answer below: -a radioactive substance -a salt solution -an external beam of radiation -a substance that chemically attacks cancer cells

Correct answer: a radioactive substance A cancer patient may receive internal radiation therapy (brachytherapy) from a radioactive substance that has been introduced into the body.

A compound may be used as a radioactive tracer if __________. Select the correct answer below: -no atoms need to be replaced with a radioisotope -at least one of the atoms is replaced with a radioisotope in the compound -at least three atoms are replaced with radioisotopes in the compound -all the atoms are replaced with radioisotopes in the compound

Correct answer: at least one of the atoms is replaced with a radioisotope in the compound We can track with a radioactive tracer or radioactive label by monitoring radioactive emissions if at least one of the atoms is replaced with a radioisotope in a compound. More than one of the atoms may be replaced.

Which is NOT a common radioactive tracer? Select the correct answer below: -technetium-99 -cobalt-60 -thallium-201 -iodine-131

Correct answer: cobalt-60 Cobalt-60 is used for radiation therapy, not radioactive tracing.

Select the response that best answer the following sentence: Gamma rays emitted by the technetium-99 isotopes can determine _____________. Select the correct answer below: -damaged tissues in the lungs -damaged tissues in the liver -damaged tissues in the heart -damaged tissues in the heart, liver, and lungs

Correct answer: damaged tissues in the heart, liver, and lungs Damaged tissues in the heart, liver, and lungs absorb certain compounds of technetium-99 preferentially. After it is injected, the location of the technetium compound can be determined by detecting the γ-rays emitted by the technetium-99.

What radioactive isotope is transported to sites for generating technetium-99m? Select the correct answer below: -molybdenum-99 -uranium-235 -thallium-201 -cobalt-60

Correct answer: molybdenum-99 The parent nuclide Mo-99 is usually transported as the molybdate ion, MoO2−4. When it decays, it forms the pertechnetate ion, TcO2−4, which contains Tc-99m.

Radioisotopes used in medicine typically have __________ half-lives. Select the correct answer below: -long -short -medium -medium to long

Correct answer: short Radioisotopes used in medicine typically have short half-lives. For example, Tc-99m has a half-life of only 6.01 hours, making it essentially impossible to store and prohibitively expensive to transport, so it is made on-site instead.

Hospitals and other medical facilities use molybdenum-99 for generation of what radioactive isotope? Select the correct answer below: -iodine-131 -technetium-99m -thallium-201 -sodium-24

Correct answer: technetium-99m Molybdenum-99 has a half-life of 66 hours and can be easily transported over long distances to hospitals or medical facilities, where its decay product technetium-99m is chemically extracted and used for imaging or therapy.

Which of the following statements is NOT true? -Exposure to radioactive emissions do not have a cumulative effect on the body during a person's lifetime. -Exposure to radioactive emissions can have a direct effect on the body. -Exposure to high levels of radiation can lead to sudden death. None of the above statements are false.

Exposure to radioactive emissions do not have a cumulative effect on the body during a person's lifetime. -Exposure to radioactive emissions can have a direct effect on the body; a sudden exposure to high levels can even lead to death. Additionally, exposure to radiation has a cumulative effect on the body during a persons lifetime; exposures can add up. Therefore, choice A is the incorrect statement.

A sample of iodine-131 was used in a procedure 24 days ago and now 1.50 mCi remain. What was the size of the original sample? (Iodine-131 has a half life of 8 days.) Use three significant figures in your answer.

First, figure out how many half-lives have elapsed. 24 days×1 half-life8 days=3 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 1.50 mCi→3.00 mCi→6.00 mCi→12.0 mCi The original amount contained 12.0 mCi.

A sample of carbon-14 has been decaying for 28,650 years and is now 35.0 grams. What was the size of the original sample? (The half-life of carbon-14 is 5,730 years.) Use three significant figures in your answer.

First, figure out how many half-lives have elapsed. 28,650 years×1 half-life5,730 years=5 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 35.0 grams→70.0 grams→140. grams→280. grams→560. grams→1120 grams The original amount contained 1120 grams.

Which of the following best describes the process of gamma (γ) emission?

Gamma (γ) emission is the decay of an excited-state nuclide accompanied by emission of a γ ray.

Health Effects of Radiation Exposure (REM)Health EffectTime to Onset (without treatment) 5 to 10changes in blood chemistry— 50nauseahours 55fatigue— 70vomiting— 75hair loss2 to 3 weeks 90diarrhea— 100hemorrhage— 400possible deathwithin 2 months 1000destruction of intestinal lining— 1000internal bleeding— 1000death1 to 2 weeks 2000damage to central nervous system— 2000loss of consciousnessminutes 2000deathhours to days Use the table above to answer the following question. A patient arrives at the hospital having been exposed to a large dose of radiation in an accident at a power plant. The patient has been vomiting and complains of diarrhea. What is a reasonable estimate you can make about the patient's exposure level from the accident?

at least 90REM -According to the table, vomiting is a likely symptom after about 75REM, and diarrhea is a likely symptom after about 90REM, so the patient was probably exposed to at least 90REM, and the dosage might have been much higher.

Which of the following has the highest density? -ionic solid -atom -atomic nucleus -these are equally dense

atomic nucleus

Which of the following is included in nuclide symbols, but is not strictly necessary for the identification of the nuclide?

atomic number

Which statement can be made that applies to all forms of radioactive decay processes? (Select all that apply.) Select all that apply: -The parent nuclide undergoes a change in atomic number as it decays to form a daughter nuclide. -The parent nuclide undergoes decay to form a daughter nuclide because it is unstable. -Radiation is emitted as a parent nuclide decays to form a daughter nuclide. -The daughter nuclide resulting from radioactive decay has less mass than the parent nuclide.

b and c

Which type of radioactive decay process is more likely than the others to occur in the unstable nucleus P1534? Select the correct answer below: -Beta decay -Electron capture -Alpha decay -Positron emission

beta decay