Question 1

In a Geiger counter, which is used to detect radioactivity, a particle produced by radioactive decay ________

Accepted Answer

When a particle produced by radioactive decay enters a Geiger counter, it ionizes an inert gas such as neon or argon, which produces a pulse of electrical current. This pulse is detected and amplified by the Geiger counter, and can be used to determine the level of radioactivity present.

Question 2

The half-life of a radioactive isotope is 1.0 minute. In an experiment, the number of decay events was monitored in 1-minute intervals over a 5-minute period. What would you predict for the most likely observations if 50 decay events were observed in the first minute? In the second minute, ________ events were observed, and in the last minute, ________ events were observed.

Accepted Answer

The half-life of a radioactive isotope is the time it takes for half of the radioactive atoms to decay. Therefore, if 50 decay events were observed in the first minute, it is expected that approximately half of that amount, or 25 decay events, would be observed in the second minute. By the fifth minute, the number of decay events would have halved approximately four more times (since the first observation), leading to a significantly reduced number of decay events. The option that best fits this pattern is 25 decay events in the second minute and 3 decay events in the last minute, reflecting the exponential decay characteristic of radioactive substances.

Question 3

Common activity levels of radon-222 are in the range of 1 picocurie/liter (pCi/L) at room temperature and pressure. How many atoms of radon decay each minute in a 1 L sample of gas with radiation at this level? Recall that 1 Bq = 1 decay/s and 1 Ci = 3.7 $\times$ 10¹⁰Bq.

Accepted Answer

1 picocurie (pCi) is equal to 3.7 decays per second. Therefore, in one minute (60 seconds), 3.7 decays/second * 60 seconds = 222 decays. Since the question asks for the number of atoms decaying each minute, the closest integer value is 2 decays per minute.

Question 4

Plutonium-238 is an $\alpha$ emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it was once used as a very reliable electrical energy source for cardiac pacemakers. What is the product of the radioactive decay of plutonium-238?

Accepted Answer

Plutonium-238 undergoes alpha decay to become uranium-234. Alpha decay involves the emission of an alpha particle (2 protons and 2 neutrons), which reduces the atomic number by 2 (from 94 to 92) and the mass number by 4 (from 238 to 234).

Question 5

Tritium (³H) is used in glowing "EXIT" signs conveniently located where there is no electricity for lightbulbs. What decay route is likely for tritium?

Accepted Answer

Tritium is a radioactive isotope of hydrogen and decays through beta decay, where a neutron is converted to a proton, an electron, and an electron antineutrino. This results in the emission of a beta particle (F1F1F1S1β) and the formation of an isotope of helium-3 (H3). Therefore, the most likely decay route for tritium is (F1F1F1S1βF1F1F10 emission), which is option B.

Question 6

Fluorine-18 is an isotope commonly used in radioimaging, due in part to the short half-life (~2 hours) of the isotope. What type of emission process is likely for fluorine-18?

Accepted Answer

Fluorine-18 has an excess of protons, making it unstable. Therefore, it is likely to undergo beta decay, specifically positron emission. The emission of a positron allows the fluorine-18 to become a stable oxygen isotope through the conversion of a proton into a neutron.

Question 7

A person's body generates about 0.2 $\mu$Ci of radioactivity! Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 $\times$ 10¹⁰ Bq and 1 Bq = 1 decay/s)

Accepted Answer

Each person emits 0.2 μCi of radioactivity. To find the total radioactivity emitted by 300 students, first convert the radioactivity per person to becquerels (Bq) since 1 Ci = 3.7 × 10^10 Bq and 1 μCi = 3.7 × 10^4 Bq. Therefore, 0.2 μCi = 0.2 × 3.7 × 10^4 Bq = 7.4 × 10^3 Bq per person. For 300 students, the total radioactivity is 300 × 7.4 × 10^3 Bq = 2.22 × 10^6 Bq, which is 2 × 10^6 decays/s when rounded to one significant figure.

Question 8

Radiation seed therapy is a common method for treating some prostate cancers and brain tumors. Iodine-125, which decays by electron capture followed by gamma ray emission with a half-life of 59.4 days, is one isotope used for this treatment. If a tumor were seeded with 1.00 $\mu$g of iodine-125 (124.90 g/mol), what would the initial radioactivity level be? Note: 1 Ci = 3.70 $\times$ 10¹⁰/s.

Accepted Answer

The initial radioactivity level can be calculated using the decay law, which relates the activity (A) of a radioactive substance to its quantity and half-life. The activity A is given by the formula A = (λN), where λ is the decay constant and N is the number of atoms. The decay constant λ can be calculated from the half-life (T1/2) using λ = ln(2)/T1/2. First, we find the number of moles of Iodine-125 in 1.00 µg, then calculate the number of atoms, and finally, use the decay constant to find the activity in decays per second, converting it to curies (Ci) at the end.1. Calculate moles of Iodine-125: (1.00 µg) / (124.90 g/mol) = 1.00 x 10^-6 g / 124.90 g/mol = 8.0064 x 10^-9 mol.2. Calculate number of atoms: 8.0064 x 10^-9 mol x (6.022 x 10^23 atoms/mol) = 4.821 x 10^15 atoms.3. Calculate decay constant λ: λ = ln(2) / T1/2 = 0.693 / (59.4 days x 24 hours/day x 3600 seconds/hour) = 1.37 x 10^-7 s^-1.4. Calculate activity A: A = λN = (1.37 x 10^-7 s^-1)(4.821 x 10^15 atoms) = 6.61 x 10^8 s^-1.5. Convert activity to curies: 6.61 x 10^8 s^-1 / (3.70 x 10^10 s^-1/Ci) = 0.0179 Ci = 17.9 mCi.Rounding to the nearest tenth gives an initial radioactivity level of approximately 17.6 mCi, making choice A correct.

Question 9

Radon-222 has a half-life of 3.8 days. A sample from a basement in Colorado was analyzed 5.0 days after it was collected and found to have an activity of 0.17 Bq. What was the original activity of this sample?

Accepted Answer

Using the formula for radioactive decay
A = A0 * (1/2)^(t/T)
where A is the activity of the sample at the time of measurement,
A0 is the original activity of the sample,
t is the time elapsed between collection and measurement, and
T is the half-life of the radionuclide.

Substituting the given values, we get
0.17 Bq = A0 * (1/2)^(5/3.8)
Solving for A0, we get A0 = 0.42 Bq (rounded to two significant figures). Therefore, the correct answer is C.

Question 10

Polonium-210 is a radioactive isotope that was used as a fatal toxin in the poisoning of Alexander Litvinenko, a former KGB agent, in 2006. What type of emission process is likely for this isotope?

Accepted Answer

Polonium-210 undergoes alpha decay, emitting alpha particles as it transforms into a different element.

Question 11

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s). An older unit for activity is the curie (1 Ci = 3.70 $\times$ 10¹⁰/s). What is the activity in Bq of a sample with an activity of 47 $\mu$ Ci of radiation?

Accepted Answer

The answer of The activity of a radioactive sample is...

Question 12

Which statement A-D, regarding the activity of a radioactive sample, is not correct?

Accepted Answer

All statements A-D are correct regarding the activity of a radioactive sample. Activity indeed measures decay events per second, depends on the decay constant and the amount of radioisotope present, follows first-order kinetics, and halves over a period defined by ln(2)/k.

Question 13

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s). An older unit for activity is the curie (1 Ci = 3.70 $\times$ 10¹⁰/s). What is the activity in $\mu$ Ci of a sample with an activity of 2.1 10 ⁵ Bq of radiation?

Accepted Answer

The answer of The activity of a radioactive sample is...

Question 14

Radiation seed therapy is a common method for treating some prostate cancers and brain tumors. Palladium-103, which decays by electron capture and gamma ray emission with a half-life of 17.0 days, is one isotope used for this treatment. How much palladium-103 (102.91 g/mol) is needed to produce an initial radioactivity level of 1.30 mCi? Note: 1 Ci = 3.70 $\times$ 10¹⁰/s.

Accepted Answer

The correct answer is A because 0.0174 µg of palladium-103 is needed to produce an initial radioactivity level of 1.30 mCi.

Question 15

When a positron and an electron collide, they ________

Accepted Answer

When a positron and an electron collide, they annihilate each other and produce gamma rays. This is because a positron is the antiparticle of an electron, and when they come in contact, they can annul each other through a process called annihilation. This process converts their mass into pure energy, which is emitted in the form of gamma rays.

Question 16

Strontium-90 is most likely to decay by ________

Accepted Answer

Strontium-90 is a beta emitter, meaning it emits a beta particle during radioactive decay. This is because there is an excess of neutrons in the nucleus, causing one of them to be converted into a proton and emit an electron (beta particle) and an antineutrino.

Question 17

Strontium-88 is the most abundant stable isotope. Strontium-90 is a particularly hazardous radioactive isotope because, as an alkali earth metal, it will substitute for calcium in bones and teeth. Predict its decay pathway.

Accepted Answer

Strontium-90 is known to undergo beta decay, where a neutron within its nucleus is converted to a proton and an electron (beta particle) is emitted from the nucleus. This results in the formation of yttrium-90, which is also unstable and undergoes further beta decay until stable zirconium-90 is formed.

Question 18

Radiation seed therapy is a common method for treating some prostate cancers and brain tumors. Cesium-131, which decays by electron capture and gamma ray emission with a half-life of 9.69 days, is a new isotope proposed for such treatment. If a tumor were seeded with 1.00 $\mu$g of cesium-131 (130.91 g/mol), what would the initial radioactivity level be? Note: 1 Ci = 3.70 $\times$ 10¹⁰/s.

Accepted Answer

The answer of Radiation seed therapy is a common method...

Question 19

Which of the following are devices that can be used to detect or measure radioactivity levels?

Accepted Answer

Scintillation counters and Geiger counters can be used to detect or measure radioactivity levels, while chromatographs are not typically used for this purpose. Therefore, choice D, "both A and C" is the best answer.

Question 20

Small traces of radioactive substances, mainly from the food we eat, are present in the human body. The most abundant radioisotope in the body is potassium-40. A person weighing 70 kg contains about 150 g of potassium, and about 0.01% of this amount is potassium-40. The half-life of potassium-40 is 1.25 $\times$10⁹ years. Estimate the rate at which radiation is produced by the decay of potassium-40 in the body.

Accepted Answer

The rate of radiation produced by the decay of potassium-40 in the body can be estimated using the formula for radioactive decay, which involves the half-life of the isotope and the amount present in the body. Given that a 70 kg person has about 150 g of potassium, and 0.01% of this is potassium-40, we calculate the amount of potassium-40 as 0.01% of 150 g = 0.015 g. Using the half-life of potassium-40 (1.25 billion years) and converting it into seconds, we can calculate the decay rate. The correct calculation leads to approximately 4,000 decays per second, which is a typical value for the human body's background radiation from potassium-40.

Quiz 19: Nuclear Chemistry: Applications to Energy and Medicine

In a Geiger counter, which is used to detect radioactivity, a particle produced by radioactive decay ________

Common activity levels of radon-222 are in the range of 1 picocurie/liter (pCi/L) at room temperature and pressure. How many atoms of radon decay each minute in a 1 L sample of gas with radiation at this level? Recall that 1 Bq = 1 decay/s and 1 Ci = 3.7 $\times$ 10¹⁰Bq.

Plutonium-238 is an $\alpha$ emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it was once used as a very reliable electrical energy source for cardiac pacemakers. What is the product of the radioactive decay of plutonium-238?

Tritium (³H) is used in glowing "EXIT" signs conveniently located where there is no electricity for lightbulbs. What decay route is likely for tritium?

Fluorine-18 is an isotope commonly used in radioimaging, due in part to the short half-life (~2 hours) of the isotope. What type of emission process is likely for fluorine-18?

A person's body generates about 0.2 $\mu$ Ci of radioactivity! Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 $\times$ 10¹⁰ Bq and 1 Bq = 1 decay/s)

Radon-222 has a half-life of 3.8 days. A sample from a basement in Colorado was analyzed 5.0 days after it was collected and found to have an activity of 0.17 Bq. What was the original activity of this sample?

Polonium-210 is a radioactive isotope that was used as a fatal toxin in the poisoning of Alexander Litvinenko, a former KGB agent, in 2006. What type of emission process is likely for this isotope?

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s) . An older unit for activity is the curie (1 Ci = 3.70 $\times$ 10¹⁰/s) . What is the activity in Bq of a sample with an activity of 47 $\mu$ Ci of radiation?

Which statement A-D, regarding the activity of a radioactive sample, is not correct?

When a positron and an electron collide, they ________

Strontium-90 is most likely to decay by ________

Strontium-88 is the most abundant stable isotope. Strontium-90 is a particularly hazardous radioactive isotope because, as an alkali earth metal, it will substitute for calcium in bones and teeth. Predict its decay pathway.

Which of the following are devices that can be used to detect or measure radioactivity levels?

Quiz 19: Nuclear Chemistry: Applications to Energy and Medicine

In a Geiger counter, which is used to detect radioactivity, a particle produced by radioactive decay ________

Common activity levels of radon-222 are in the range of 1 picocurie/liter (pCi/L) at room temperature and pressure. How many atoms of radon decay each minute in a 1 L sample of gas with radiation at this level? Recall that 1 Bq = 1 decay/s and 1 Ci = 3.7 ×\times× 1010 Bq.

Plutonium-238 is an α\alphaα emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it was once used as a very reliable electrical energy source for cardiac pacemakers. What is the product of the radioactive decay of plutonium-238?

Tritium (3H) is used in glowing "EXIT" signs conveniently located where there is no electricity for lightbulbs. What decay route is likely for tritium?

Fluorine-18 is an isotope commonly used in radioimaging, due in part to the short half-life (~2 hours) of the isotope. What type of emission process is likely for fluorine-18?

A person's body generates about 0.2 μ\muμ Ci of radioactivity! Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 ×\times× 1010 Bq and 1 Bq = 1 decay/s)

Radon-222 has a half-life of 3.8 days. A sample from a basement in Colorado was analyzed 5.0 days after it was collected and found to have an activity of 0.17 Bq. What was the original activity of this sample?

Polonium-210 is a radioactive isotope that was used as a fatal toxin in the poisoning of Alexander Litvinenko, a former KGB agent, in 2006. What type of emission process is likely for this isotope?

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s) . An older unit for activity is the curie (1 Ci = 3.70 ×\times× 1010/s) . What is the activity in Bq of a sample with an activity of 47 μ\muμ Ci of radiation?

Which statement A-D, regarding the activity of a radioactive sample, is not correct?

When a positron and an electron collide, they ________

Strontium-90 is most likely to decay by ________

Strontium-88 is the most abundant stable isotope. Strontium-90 is a particularly hazardous radioactive isotope because, as an alkali earth metal, it will substitute for calcium in bones and teeth. Predict its decay pathway.

Which of the following are devices that can be used to detect or measure radioactivity levels?

Common activity levels of radon-222 are in the range of 1 picocurie/liter (pCi/L) at room temperature and pressure. How many atoms of radon decay each minute in a 1 L sample of gas with radiation at this level? Recall that 1 Bq = 1 decay/s and 1 Ci = 3.7 $\times$ 10¹⁰Bq.

Plutonium-238 is an $\alpha$ emitter and a compact heat source. Coupled with a PbTe thermoelectric device, it was once used as a very reliable electrical energy source for cardiac pacemakers. What is the product of the radioactive decay of plutonium-238?

Tritium (³H) is used in glowing "EXIT" signs conveniently located where there is no electricity for lightbulbs. What decay route is likely for tritium?

A person's body generates about 0.2 $\mu$ Ci of radioactivity! Determine the total radioactivity emitted by 300 students in a lecture hall. (1 Ci = 3.7 $\times$ 10¹⁰ Bq and 1 Bq = 1 decay/s)

The activity of a radioactive sample is the number of decay events per second. The SI unit of activity is the becquerel (1 Bq = 1/s) . An older unit for activity is the curie (1 Ci = 3.70 $\times$ 10¹⁰/s) . What is the activity in Bq of a sample with an activity of 47 $\mu$ Ci of radiation?