Question 1

Fluorine-18, which is often used in PET scans to locate tumors, decays to form a positron and oxygen-18.After 90.0 minutes, 1.00 18O is present relative to every 1.30 18F.Estimate the half-life of F-18.

Accepted Answer

The decay of Fluorine-18 (F-18) can be analyzed using the formula for radioactive decay, $N = N_0 \times (1/2)^{t/T}$, where $N$ is the remaining quantity of the substance, $N_0$ is the initial quantity, $t$ is the time elapsed, and $T$ is the half-life of the substance. Given that after 90 minutes, the ratio of $^{18}O$ to $^{18}F$ is 1.00 to 1.30, it means that for every 2.30 parts of the mixture, 1.30 parts are $^{18}F$, implying that $^{18}F$ has decayed to 1.30/2.30 of its original amount. Solving the decay formula for $T$ with $t = 90$ minutes and $N/N_0 = 1.30/2.30$, we find that the half-life of F-18 is approximately 109 minutes.

Question 2

Cobalt-60 decays to nickel-60.What particle is emitted?

Accepted Answer

Cobalt-60 decays to nickel-60 through beta decay, where a neutron in the cobalt nucleus is converted into a proton, and a beta particle (electron) is emitted.

Question 3

When a positron and an electron collide, they

Accepted Answer

When a positron and an electron collide, they annihilate each other, converting their mass into energy in the form of gamma rays. This process is known as pair annihilation.

Question 4

Uranium-238 decays to form thorium-234 with a half-life of 4.5 * 10⁹ years.How many years will it take for 75% of the uranium-238 to decay?

Accepted Answer

After one half-life (4.5 billion years), 50% of the uranium-238 would have decayed, leaving 50%. After another half-life (another 4.5 billion years, totaling 9 billion years), half of the remaining 50% would decay, leaving 25% and meaning 75% has decayed.

Question 5

Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland.If a patient drinks a sodium iodide (NaI) solution containing iodine-131, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration?

Accepted Answer

To find the time it takes for the concentration of iodine-131 to drop to 5.0% of its initial concentration, we can use the half-life formula. The formula to calculate the number of half-lives (n) that have passed is given by: $n = \frac{\log(\text{final concentration/initial concentration})}{\log(0.5)}$. Here, the final concentration is 5% (or 0.05) of the initial concentration (100% or 1). Plugging the values into the formula gives: $n = \frac{\log(0.05)}{\log(0.5)} \approx 4.32$ half-lives. Since each half-life is 8.1 days, the total time is $4.32 \times 8.1 \approx 35$ days.

Question 6

Tritium (³H) is used in glowing "EXIT" signs located where there is no electricity for lightbulbs.If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 20.0 years?

Accepted Answer

After 20 years, approximately 1.63 half-lives have passed (20/12.26). The remaining quantity is (1/2)^1.63 ≈ 0.323 or 32.3% of the original amount.

Question 7

Sodium-22 undergoes electron capture.Identify the resulting isotope.

Accepted Answer

During electron capture, a proton in the nucleus captures an electron and turns into a neutron, decreasing the atomic number by 1 but leaving the mass number unchanged. Sodium-22 (Na-22) has an atomic number of 11. After electron capture, it becomes Neon-22 (Ne-22) with an atomic number of 10, keeping the mass number 22 the same.

Question 8

Cobalt-56 decays by emitting a positron.What is the product?

Accepted Answer

The answer of Cobalt-56 decays by emitting a positron.What is...

Question 9

Suppose 62.0% of a sample of radioactive polonium-218 remains after 2.14 minutes.Estimate the half-life of Po-218.

Accepted Answer

The half-life of a radioactive substance is the time it takes for half of the substance to decay. In this case, 62.0% of the substance remains after 2.14 minutes, which means that 38.0% of the substance has decayed. The half-life can be calculated using the formula:t1/2 = (ln 2) / kwhere t1/2 is the half-life, ln is the natural logarithm, and k is the decay constant. The decay constant can be calculated using the formula:k = (ln 2) / t1/2Substituting the given values into the formula, we get:k = (ln 2) / 2.14 minutes = 0.323 minutes^-1Substituting this value into the formula for the half-life, we get:t1/2 = (ln 2) / 0.323 minutes^-1 = 3.10 minutesTherefore, the half-life of Po-218 is 3.10 minutes.

Question 10

In 1913, an element was known to "emanate" from radium-226 by $\alpha$emission and then to decay to polonium-218, also by $\alpha$ emission.What was the unknown element?

Accepted Answer

The given information describes alpha decay from radium-226 to an unknown element, followed by another alpha decay from this unknown element to polonium-218. The only element known to alpha decay to polonium-218 is radon-222, therefore the unknown element in this scenario must be radon-222.

Question 11

Radium-226 is formed as a product when which isotope undergoes $\beta$+ emission?

Accepted Answer

Francium-226 undergoes beta decay to form radium-226.

Question 12

Phosphorus-32 is a radioactive isotope used in many biomedical applications.How much phosphorus-32 was originally used if there are only 3.50 mg left in a sample after 288 h? The half-life of phosphorus-32 is 14.3 days.)

Accepted Answer

The answer of Phosphorus-32 is a radioactive isotope used in...

Question 13

Suppose 67.5% of a sample of radioactive sodium-24 has decayed after one day.Estimate the half-life of Na-24.

Accepted Answer

The answer of Suppose 67.5% of a sample of radioactive...

Question 14

Phosphorus-32, a $\beta$-emitter, is a radioactive isotope used in many biomedical applications.How much time has passed if the ratio of 32S to 32P is 4 to 5?( The half-life of phosphorus-32 is 14.3 days.)

Accepted Answer

The answer of Phosphorus-32, a $\beta$-emitter, is a radioactive isotope...

Question 15

Which of the following statements regarding nuclear decay is NOT correct?

Accepted Answer

The statement that all nuclei of a radionuclide decay at the same rate is not correct because radioactive decay is a statistical process. Each nucleus has a certain probability of decaying, but they do not all decay at the same moment or rate. The rate of decay is described by the half-life, which is the time required for half of a sample of a radioactive substance to decay, but this does not mean each individual nucleus decays at the same rate.

Question 16

Plutonium-238 is an $\alpha$ emitter.What is the product of the radioactive decay of Pu-238?

Accepted Answer

Plutonium-238 undergoes alpha decay, which means it emits an alpha particle (2 protons and 2 neutrons). This reduces its atomic number by 2 (from 94 to 92) and its mass number by 4 (from 238 to 234), resulting in uranium-234.

Question 17

A half-life is

Accepted Answer

The half-life of a radioactive substance is the time required for one-half of the atoms of a radioactive isotope to decay into another element, not the time for all of a population to die, half of the lifetime of an unstable nucleus, a constantly changing value, or independent of the decay rate constant.

Question 18

Nitrogen-13 decays by positron emission to produce

Accepted Answer

Nitrogen-13 decays by positron emission, which decreases the atomic number by one, resulting in carbon-13.

Question 19

The half-life of chromium-51 is 27.8 days.How many half-lives have elapsed after one year?

Accepted Answer

One year is approximately 365 days. Dividing 365 by the half-life of 27.8 days gives approximately 13.1 half-lives.

Question 20

Radon-220 decays to polonium-216.What particle is emitted?

Accepted Answer

Radon-220 decays to polonium-216 through alpha decay, which involves the emission of an alpha particle (two protons and two neutrons, equivalent to a helium-4 nucleus).

Quiz 21: Nuclear Chemistry the Risks and Benefits

Fluorine-18, which is often used in PET scans to locate tumors, decays to form a positron and oxygen-18.After 90.0 minutes, 1.00 18O is present relative to every 1.30 18F.Estimate the half-life of F-18.

Cobalt-60 decays to nickel-60.What particle is emitted?

When a positron and an electron collide, they

Uranium-238 decays to form thorium-234 with a half-life of 4.5 * 10⁹ years.How many years will it take for 75% of the uranium-238 to decay?

Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland.If a patient drinks a sodium iodide (NaI) solution containing iodine-131, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration?

Tritium (³H) is used in glowing "EXIT" signs located where there is no electricity for lightbulbs.If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 20.0 years?

Sodium-22 undergoes electron capture.Identify the resulting isotope.

Cobalt-56 decays by emitting a positron.What is the product?

Suppose 62.0% of a sample of radioactive polonium-218 remains after 2.14 minutes.Estimate the half-life of Po-218.

In 1913, an element was known to "emanate" from radium-226 by $\alpha$ emission and then to decay to polonium-218, also by $\alpha$ emission.What was the unknown element?

Radium-226 is formed as a product when which isotope undergoes $\beta$ + emission?

Phosphorus-32 is a radioactive isotope used in many biomedical applications.How much phosphorus-32 was originally used if there are only 3.50 mg left in a sample after 288 h? The half-life of phosphorus-32 is 14.3 days.)

Suppose 67.5% of a sample of radioactive sodium-24 has decayed after one day.Estimate the half-life of Na-24.

Phosphorus-32, a $\beta$ -emitter, is a radioactive isotope used in many biomedical applications.How much time has passed if the ratio of 32S to 32P is 4 to 5?( The half-life of phosphorus-32 is 14.3 days.)

Which of the following statements regarding nuclear decay is NOT correct?

Plutonium-238 is an $\alpha$ emitter.What is the product of the radioactive decay of Pu-238?

A half-life is

Nitrogen-13 decays by positron emission to produce

The half-life of chromium-51 is 27.8 days.How many half-lives have elapsed after one year?

Radon-220 decays to polonium-216.What particle is emitted?

Quiz 21: Nuclear Chemistry the Risks and Benefits

Fluorine-18, which is often used in PET scans to locate tumors, decays to form a positron and oxygen-18.After 90.0 minutes, 1.00 18O is present relative to every 1.30 18F.Estimate the half-life of F-18.

Cobalt-60 decays to nickel-60.What particle is emitted?

When a positron and an electron collide, they

Uranium-238 decays to form thorium-234 with a half-life of 4.5 * 109 years.How many years will it take for 75% of the uranium-238 to decay?

Iodine-131 has a half-life of 8.1 days and is used as a tracer for the thyroid gland.If a patient drinks a sodium iodide (NaI) solution containing iodine-131, how many days will it take for the concentration of iodine-131 to drop to 5.0% of its initial concentration?

Tritium (3H) is used in glowing "EXIT" signs located where there is no electricity for lightbulbs.If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 20.0 years?

Sodium-22 undergoes electron capture.Identify the resulting isotope.

Cobalt-56 decays by emitting a positron.What is the product?

Suppose 62.0% of a sample of radioactive polonium-218 remains after 2.14 minutes.Estimate the half-life of Po-218.

In 1913, an element was known to "emanate" from radium-226 by α\alphaα emission and then to decay to polonium-218, also by α\alphaα emission.What was the unknown element?

Radium-226 is formed as a product when which isotope undergoes β\betaβ + emission?

Phosphorus-32 is a radioactive isotope used in many biomedical applications.How much phosphorus-32 was originally used if there are only 3.50 mg left in a sample after 288 h? The half-life of phosphorus-32 is 14.3 days.)

Suppose 67.5% of a sample of radioactive sodium-24 has decayed after one day.Estimate the half-life of Na-24.

Phosphorus-32, a β\betaβ -emitter, is a radioactive isotope used in many biomedical applications.How much time has passed if the ratio of 32S to 32P is 4 to 5?( The half-life of phosphorus-32 is 14.3 days.)

Which of the following statements regarding nuclear decay is NOT correct?

Plutonium-238 is an α\alphaα emitter.What is the product of the radioactive decay of Pu-238?

A half-life is

Nitrogen-13 decays by positron emission to produce

The half-life of chromium-51 is 27.8 days.How many half-lives have elapsed after one year?

Radon-220 decays to polonium-216.What particle is emitted?

Uranium-238 decays to form thorium-234 with a half-life of 4.5 * 10⁹ years.How many years will it take for 75% of the uranium-238 to decay?

Tritium (³H) is used in glowing "EXIT" signs located where there is no electricity for lightbulbs.If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 20.0 years?

In 1913, an element was known to "emanate" from radium-226 by $\alpha$ emission and then to decay to polonium-218, also by $\alpha$ emission.What was the unknown element?

Radium-226 is formed as a product when which isotope undergoes $\beta$ + emission?

Phosphorus-32, a $\beta$ -emitter, is a radioactive isotope used in many biomedical applications.How much time has passed if the ratio of 32S to 32P is 4 to 5?( The half-life of phosphorus-32 is 14.3 days.)

Plutonium-238 is an $\alpha$ emitter.What is the product of the radioactive decay of Pu-238?