CHEM

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. 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

- 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.

32P is an isotope that is sometimes used as a marker in biochemical applications. It has a half-life of about 14.29 days. What is the rate constant for it's nuclear decay? 0.04851 days−1 0.1400 days−1 0.04851 s−1 0.1400 s−1

0.04851 days−1 The half-life is related to the first order rate constant, k, by the equation t12=ln2k. To find k from the half-life, solve this equation for k. Then substitute in in the half-life, and note that the rate constant and the half-life must have consistent units. k=ln2t12=ln214.29 days=0.04851 days−1

A first-order reaction has a rate constant k of 3.88 hr−1. If the initial concentration of the reactant is 4.25 M, what is the half-life of the reaction?

0.179 hr For a first-order reaction, we can use t 1/2= ln 2 / k Substituting for the value of k, we have t1/2 = ln2 / 3.88 hr−1 ≈ 0.179 hr Notice that the initial concentration of the reactant does not affect what the value of the half-life is.

A person absorbs 0.00023J/g tissue of γ-radiation. How much is this in sieverts (Sv)?

0.23 Sv Notice that the absorption is given in Joules per gram and 1 Gy= 1 J/kg tissue. Convert the absorption to grays, then convert the grays to sieverts, using the equivalence Sv = RBE × Gy. 0.00023 Jg tissue × 1000 g/kg = 0.23 J/kg tissue=0.23 Gy Since the RBE for γ-radiation is 1, the number of sieverts is the same as the number of grays. Therefore, 0.00023J/g tissue of γ-radiation is equivalent to 0.23Sv.

A worker in a high-energy particle accelerator facility is inadvertently exposed to 52rem of proton radiation. What is the number of grays (Gy) to which this is equivalent? Use a relative biological effectiveness of 2 for proton radiation.

0.26 Gy First, convert rem to rad. The radiation dose in rads and the roentgen equivalent for man (rem) are related by the following equation, where RBE is the relative biological effectiveness. Recall that the RBE for proton radiation is 2. number of rems = RBE×number of rads 52 rems = 2 × number of rads Therefore, 52rem will equal 26rad in this case. Then convert rads to grays using the equivalence 1Gy=100rad. 26rad×(1Gy100rad)=0.26Gy

The rate constant of the first-order reaction A→4B+2C is 0.600 s−1. What is the half-life of the reaction given that [A]0=0.567 mol L−1?

1.155 s For a first-order reaction, we can use t1/2=ln2k Substituting for the value of k, we have t 1/2= ln 2 / 0.600s−1 ≈ 1.155 s Notice that the initial concentration of the reactant does not affect what the value of the half-life is.

When 100rem=1Sv, express 10Gy of alpha radiation in terms of rem. 10rem 100rem 1000rem 10,000rem

10,000rem Sv=RBE×Gy, where RBE is the relative biological effectiveness factor for a type of radiation. For alpha radiation, the RBE is approximately 10.Multiply the number of grays by 10. Thus, the number of sieverts is 100. It is given that 100rem=1Sv, so multiply the number of sieverts by 100. 100Sv×100remSv=10,000rem

During spontaneous fission, a nucleus of 254 98Cf can produce 11846 Pd, four neutrons, and what other nuclide?

13252Te

Carbon-14 has a half life of 5,730 years. Which of the following could be the age of a sample that was dated by its C-14 content? 17,000 yr 142,000 yr 2,980,100 yr 4,017,991,500 yr

17,000 yr Carbon dating offers accurate approximations for the dates of origin for objects that are up to 57,000 years old.

The initial concentration of A in the first-order reaction A→4B+C is 0.318 mol L−1. Given that the rate constant is 0.31 s−1, what is the half-life of the reaction? 0.51 s 1.1 s 2.2 s 10 s

2.2 s The half-life of a first-order reaction is as shown below. t12 = ln2k Thus, the half-life of this reaction is as shown, rounded to two significant figures.t12 = 0.6930.31 s−1=2.2 s

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).

2.5 rem he 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

A sample of iodine-131 was used in a procedure 32 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.

23.8 mCi or 24.0 mCi

Technitium-99m is used for medical imaging applications, but it must be synthesized on-site due to its relatively short half-life of about 6.0 hr. How much of a 24 g samples of 99mTc would be remaining 18 hours after it was prepared if it is not used? 12 g 4.0 g 3.0 g 18 g

3.0 g Each time a complete half-life passes, the sample's quantity drops by one half (thus the name) regardless of the amount. 18 hr is 3.0 half-lives (because 18 hr÷6.0 hr=3.0), so the fraction of sample remaining is (1/2)3=12×12×12=18. To find the mass of 99mTc remaining in the sample, multiply the starting mass by 18. 24 g×18=3.0 g

The RBE for a particle beam is 15, and the dose of radiation delivered is 20rad. Find the dose in rem.

300 rem Find the dose in rem by multiplying the absorbed dose and the RBE. Biologically effective dose=(RBE)×(absorbed dose)=15×20= 300 rem

A 5g tumor is irradiated with high-energy X-rays and absorbs a total of 0.2J of energy. What is the absorbed dose in grays? 25Gy 35Gy 45Gy 40Gy

40Gy First, the mass of the tissue must be converted into kilograms. 5g×1kg1000g=0.005kg The dose in grays is calculated by dividing the total energy with the tissue irradiation in kilograms, and the equation isDGy=ΔEm Substitute in the values that are given.DGy=0.2J0.005kg=40Gy

A sample of carbon-14 has been decaying for 17,190 years and is now 52.0 grams. What was the size of the original sample? (The half-life of carbon-14 is 5,730 years.)

416 g First, figure out how many half-lives have elapsed. 17,190 years×1 half-life5,730 years=3 half-lives Next, to work backwards through the half-lives, doubling the amount for each: 52.0 grams→104 grams→208 grams→416 gramsThe original amount contained 416 grams.

The rem value of an absorbed dose of gamma radiation equal to 0.05JKg of tissue is __________.

5 rem Start by converting to rad. 1 rad= 0.01J/kg of tissue. Convert 0.5 J/kg of tissue into rad. 0.05 J/kg tissue ×1 rad 0.01 J/kg tissue=5rad 1rem=RBE×rad, where RBE is the relative biological effectiveness factor for a type of radiation. For gamma radiation, the RBE is approximately 1, so the rem value will be the same as the rad value.

Nuclear reactors require uranium that has been enriched to be about what percentage U-235? 1% 5% 20% 50%

5% Uranium that is approximately 5% U-235 is ideal for a nuclear reactor. With this percentage of U-235 in the uranium sample, the sample is enriched enough that a chain reaction can be sustained but not so much that supercritical mass is achieved (which could result in an explosion).

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.) 14.0 mCi 28.0 mCi 56.0 mCi 112 mCi

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.

Nitrogen-13 is an unstable isotope with a decay constant k=1.16×10−3 s−1. What is its half-life? 8.04×10−3 s 6.76 s 1720 s 598 s

598 s Unstable isotopes decay by first order kinetics, and their half-lives can be calculated using the formula t1/2=ln2k. Substitute 1.16×10−3 s−1 for k and solve for t1/2. t1/2=ln2k=ln21.16×10−3 s−1=598 s

The percentage of the fuel in a nuclear fission reactor that remains in the fuel rods as fission products and unused fuel is _______ Select the correct answer below: 50% 99.9% 100% 0.3%

99.9% Only about 0.01% of the mass of fuel in a nuclear fission reactor is used, leaving 99.9% of the fuel rods as fission products and unused fuel.

It is the emission of an α particle from the nucleus. An α particle is a helium nucleus (2 protons and 2 neutrons) that is ejected from an unstable nucleus

Alpha (α) decay

If mercury-201 undergoes electron capture, what nuclide will result?

Au - 201 We add up the mass numbers on the left side to obtain a total mass of 201, and sum the charges on this side to obtain a total charge of 79. Thus by subtraction we deduce that the unknown nuclide must have a mass of 201 and an atomic number (charge) of 79. The element with this particular atomic number is gold, and the isotope is gold-201. Therefore, the unknown nuclide must be Au79201.

What nuclide, when bombarded by an α particle, will generate carbon-12 and a neutron?

Be - 9 The nuclear reaction is as follows: XZA+He24⟶n01+C612 We add up the mass numbers on the right side to obtain a total mass of 13, and sum the charges on this side to obtain a total charge of 6. On the left side, the α particle (or He nucleus) has a mass of 4 and a nuclear charge of 2; thus by subtraction we deduce that the unknown nuclide must have a mass of 9 and an atomic number (charge) of 4. The element with this particular atomic number is beryllium, and the isotope is beryllium-9. Therefore, the unknown nuclide must be Be49.

Increase the number of its protons and decrease the number of its neutrons. It is the emission of an electron from a nucleus

Beta (β) decay

Which of the following radioactive isotopes has the shortest half-life? Great work! That's correct. Uranium-238 Carbon-14 Potassium-40 Rubidium-87

Carbon-14 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 carbon-14 has the shortest half-life.

Occurs when one of the inner electrons in an atom is captured by the atom's nucleus. Atomic number decreases.

Electron capture

In radioactive decay, the parent nuclide is unstable and decays into the smaller nuclide, which often times does not undergo further decay. Select the correct answer below: True False

False The spontaneous change of an unstable nuclide into another is radioactive decay. The unstable nuclide is a larger nuclide, and the nuclide that results from the decay are smaller nuclide. The smaller nuclide may be stable, or it may decay itself. The radiation produced during radioactive decay is such that the smaller nuclide lies closer to the band of stability than the parent nuclide.

It is observed when an isotope is formed in an excited state. There is no change in mass number or atomic number during the emission of a γ ray unless the γ emission accompanies one of the other modes of decay.

Gamma emission (γ emission)

Which of the following are able to absorb neutrons without undergoing fission? (select all that apply) Select all that apply: Hafnium Cadmium Plutonium Uranium

Hafnium Cadmium Boron, cadmium, and hafnium are all able to absorb neutrons without fissioning.

Which of the following is true of positron emission ? It increases the nuclide's atomic number by 1. It decreases the nuclide's neutron:proton (n:p) ratio. It decreases the nuclide's mass number by 1. It increases the nuclide's neutron:proton (n:p) ratio.

It increases the nuclide's neutron:proton (n:p) ratio. - If there are too many protons in the nucleus, positron emission can occur. This involves the conversion of a proton into a neutron, which decreases the atomic number by 1 and increases the neutron:proton (n:p) ratio.

How is cobalt-60 obtained for use in radiation treatment? 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.

It is prepared by irradiating cobalt-59 with neutrons.

How is cobalt-60 obtained for use in radiation treatment? 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.

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

Is a particle of matter that is the same mass of an electron, but it has the opposite charge

Positron

Is the emission of a positron from the nucleus. Positron decay is the conversion of a proton into a neutron with the emission of a positron. Decreases the atomic number.

Positron emission (β+ decay)

Which of the following CANNOT be produced from the fission of uranium-236? Cs-137 Br-87 Pu-239 La-136

Pu-239 Plutonium-239 is a larger nuclide than uranium-236; therefore, this cannot be a product of the fission of U-236.

Which unit of measurement would give the most complete information on absorbed dose? Curie (Ci) Becquerel (Bq) Radiation Absorbed Dose (RAD) Sievert (Sv)

Radiation Absorbed Dose (RAD) The radiation absorbed dose (RAD) quantifies the energy absorbed per kilogram of tissue and has units of J/kg tissue. The curie and becquerel measure emission and the sievert (Sv), along with a REM (Roentgen Equivalent for Man), take in to account the biologically effective dose for radiation that measures the relative damage done by radiation.

The spontaneous change of an unstable nucleus into another is

Radioactive decay. - The process reduces the energy of the nucleus and produces radiation.

If radium-226 undergoes α emission, what nucleus is produced?

Rn - 222 The left side has a total mass of 226 and a total nuclear charge of 88. On the right side, the α particle has a mass of 4 and a charge of 2; thus, by subtraction the unknown nuclide must have a mass of 222 and an atomic number (charge) of 86. The element with this particular atomic number is radon, and the isotope is radon-222. Therefore, the unknown nuclide must be Rn86222.

Which unit of radiation measurement takes into account the relative damage done by the radiation? Becquerel (Bq) Gray (Gy) Sievert (Sv) Curie (Ci)

Sievert (Sv)

In a nuclear reaction, what is rearranged? Chemical bonds Electrons Atoms Subatomic particles

Subatomic particles

Which of these is a nucleus that can be used for radiometric dating? Correct! You nailed it. Fe-50 S-32 U-238 all of the abov

U-238 Uranium-238, with a half life of about 4.5 billion years, can be used to date extremely old rocks. S-32 is a stable nucleus (it never decays), and Fe-50 does not exist.

There are no self-sustaining fusion reactors operating in the world because there is currently a lack of _______. a way to achieve the extremely high temperatures needed for a fusion reaction a method to dispose of the waste produced by fusion reactions a way to contain fusion reactions materials that will participate in fusion

a way to contain fusion reactions There are no self-sustaining fusion reactors operating in the world because there is currently a lack of a way to contain fusion reactions. There are small-scale controlled fusion reactions that have been run for very brief periods.

At temperatures at which useful fusion reactions occur: most molecules dissociate into atoms, which then ionize to form plasma all molecules dissociate into atoms, which then ionize to form plasma ions neutralize to form atoms, which then combine to form molecules none of the above

all molecules dissociate into atoms, which then ionize to form plasma At temperatures (those at or above 15,000,000 K) at which useful fusion reactions occur, molecules dissociate into atoms, which then ionize to form plasma.

A compound may be used as a radioactive tracer if __________. 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

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

atomic nucleus The atomic nucleus is extremely dense compared to ionic solids, and certainly more dense than the atom taken as a whole (which is mostly empty space).

When the number of fission reactions ocurring in a bomb increases at an exponential rate, this phenomenon is called a(n): exponential fission chain reaction bulk fission none of the above

chain reaction In a nuclear chain reaction, the neutrons produced from the initial fission reaction continue to bombard the nuclei and initiate an ever-increasing number of fission reactions. The rate of fission within the system thus increases exponentially as the chain reaction proceeds.

A nuclear explosion in a reactor can occur as the result of the failure of which of the following processes? Well done! You got it right. containment cooling generation of electricity steam generation

containment cooling A nuclear explosion can occur if the reactor's cooling and/or containment systems fail, causing an out-of-control reaction or a nuclear meltdown.

Identify the source of radiation that humans have increasing exposure to when taking airplane flights. strontium-90 cosmic rays carbon-14 potassium-40

cosmic rays Humans have increased exposure to cosmic rays, which contain protons, alpha particles, and other radiation, when taking airplane flights because cosmic rays are more prevalent in the upper atmosphere than on the ground.

n order to explode, an atomic bomb requires a mass of fissionable material above the: subcritical mass critical mass supercritical mass mass defect

critical mass In order to initiate fission, the amount of fissile material must be above the critical mass. If there is less than the critical mass, the reaction will not continue.

If you are measuring radioactive emission for a medical application, what would be an appropriate unit of measurement? sievert (Sv) Roentgen equivalent man (rem) gray (Gy) curie (Ci)

curie (Ci) Curies (Ci) would be an appropriate unit to measure radioactive decays or emissions. The curie (Ci) is frequently used in medicine rather than the SI unit, becquerel, although they measure the same thing. Grays quantify exposure to radiation, while sieverts and rems are units of exposure scaled by the biological damage potential.

What is the main challenge in building a fusion reactor? Select the correct answer below: finding a way to contain the fusion reactions managing the energy produced by fusion finding materials to participate in fusion none of the above

finding a way to contain the fusion reactions No material can withstand the temperatures required for fusion without breaking down, so containment of fusion reactions requires creative approaches like containment by magnetic field or focused lasers.

Which of the following generates the most energy? combustion fission fusion each of these processes generates about the same amout of energy

fusion Nuclear fusion produces significantly more energy than fission, and both produce a great deal more energy than combustion.

Which unit involves the measurement of the energy of the absorbed dose? becquerel curie gray sievert

gray The gray measures the energy absorbed per kilogram of tissue. The curie and becquerel both measure emission and the sievert measures tissue damage.

The SI unit for measuring absorbed radiation dose is __________ sievert (Sv) Roentgen equivalent man (rem) gray (Gy) curie (Ci)

gray (Gy) The gray is the SI unit for measuring absorbed dose. Sieverts and rems are units for measuring dosage scaled by the potential damage to tissue. The curie is a unit for measuring decay rate.

Positron emission is most likely to occur if a nucleus: is too large has a neutron to proton ratio that is too large has a neutron to proton ratio that is too small is excited

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.

Carbon-14 forms: in the nitrogen-rich upper atmosphere in carbon-deficient environments in the depths of the ocean none of the above

in the nitrogen-rich upper atmosphere Carbon-14 forms when nitrogen-14 nuclei are bombarded by neutrons from cosmic rays arriving from space.

Heavier elements will undergo fission in order to: increase total binding energy decrease total binding energy increase binding energy per nucleon decrease binding energy per nucleon

increase binding energy per nucleon Smaller nuclei have binding energies per nucleon closer to the ideal value, so heavy elements undergo fission to produce smaller (more stable) nuclei.

α emission is most likely to occur if a nucleus: is too large has a neutron to proton ratio that is too large has a neutron to proton ratio that is too small is excited

is too large If a nucleus is simply too large to be stable, it is likely to undergo α emission, which decreases the mass of the nucleus by 4. For example, when polonium-210 undergoes α decay, the loss of an α particle leaves the daughter nuclide with a mass number four units smaller and an atomic number two units smaller than those of the parent nuclide.

The half-life of a radioisotope is 300.0 seconds. What is the rate constant k for the radioactive decay of this isotope?

k=0.00231 s−1 For a first-order reaction such as the decay of a radioisotope, we can use t 1/2 = ln 2 / k To solve for k, the equation can be rearranged to k= ln 2 / t 1/2 Given that t 1/2 = 300.0 s , 300.0 s is then substituted into this equation to solve for k. k= ln 2 / t 1/2 = ln 2300.0 s = 0.00231 s−1

Nuclear fission typically occurs for: large nuclei small nuclei nuclei just outside the band of stability all of the above

large nuclei Fission involves the splitting of large nuclei into smaller nuclei.

When balancing nuclear reactions, the mass numbers of the nuclides: must always increase must always decrease must not have a net change depends on the reaction

must not have a net change For any nuclear reaction, the sum of the masses (superscripts) of the "reactants" must be equal that of the "products". The law of conservation of mass still applies for most nuclear reactions!

What kind of decay must magnesium-23 undergo to generate sodium-23? α emission β emission positron emission gamma emission

positron emission In order for magnesium-23 to become sodium-23, the atomic number must decrease by 1 while the mass remains unchanged. This can be accomplished by the transformation of a proton into a neutron, which results in positron emission in order to conserve the overall charge.

Which of the following are devices used to measure personal exposure to radiation? quartz fiber dosimeters Geiger counters scintillation counters film badges

quartz fiber dosimeters film badges

Which of the following are devices used to detect and measure radiation? Geiger counters scintillation counters becquerels sieverts radiation dosimeters

radiation dosimeters

The SI unit measuring radiation dose is the gray (Gy). Which unit is equal to a gray scaled by the numeric factor called the relative biological effectiveness? sievert (Sv) Roentgen equivalent man (rem) radiation absorbed dose (rad) curie (Ci)

sievert (Sv) Sieverts are units for measuring dosage scaled by the potential damage to tissue. The dose is calculated by multiplying the absorbed dose in grays by the relative biological effectiveness.

An amount of fissionable material that sufficient to sustain a chain reaction at a constantly increasing rate is called a: subcritical mass critical mass supercritical mass none of the above

supercritical mass If there is enough radioactive material for the chain reaction to occur at an ever-increasing rate, the mass of this material is termed supercritical