Radioactive Decay Problems
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Questions and Answers

What is the decay constant for phosphorus-32 if its half-life is 14.26 days?

  • 0.0486 s⁻¹
  • 0.0486 d⁻¹ (correct)
  • 0.0972 d⁻¹
  • 0.0486 yr⁻¹

How much energy is released from 3.57 × 10¹² decays of beta particles with an average energy of 700 keV?

  • 0.412 J
  • 0.350 J
  • 0.400 J (correct)
  • 0.560 J

What fraction of the original nuclei remains after 30 days for palladium-103, which has a half-life of 17.0 days?

  • 0.294 (correct)
  • 0.706
  • 0.500
  • 0.350

What is the initial activity of the palladium-103 capsules required to deliver 2.12 J of gamma radiation in 30 days?

<p>5.0 MBq (A)</p> Signup and view all the answers

How many nuclei were initially present if the initial activity was 5.22 MBq for phosphorus-32?

<p>9.28 × 10¹² nuclei (D)</p> Signup and view all the answers

What is the energy in joules of a single gamma ray emitted by palladium-103 with an energy of 21.0 keV?

<p>3.36 × 10⁻¹⁵ J (A)</p> Signup and view all the answers

Which calculation correctly identifies the amount of energy absorbed during a 10.0-day period for phosphorus-32?

<p>0.400 J (B)</p> Signup and view all the answers

If 0.706 of palladium-103 has decayed after 30 days, how does this influence the total energy delivered to the tumor?

<p>Increases the dose received (C)</p> Signup and view all the answers

What is the net rate of energy absorption from radiation for a person weighing 70.0 kg, given an absorption limit of 45.5 mJ per year per kilogram?

<p>3.19 J/year (A)</p> Signup and view all the answers

Which equation represents the mass-energy equivalence in nuclear reactions?

<p>E = mc^2 (B)</p> Signup and view all the answers

In the given nuclear reaction, what is the significance of adding 92 electrons?

<p>It balances the atomic charge. (B)</p> Signup and view all the answers

What is the total energy released from decay per year when considering the decay rate and decay energy?

<p>2.27 × 10^5 J/year (C)</p> Signup and view all the answers

What does the variable λ represent in the context of decay rates?

<p>Decay constant (B)</p> Signup and view all the answers

In radioactive decay theory, $P = QR$ implies what relationship?

<p>Energy released increases with decay rate. (D)</p> Signup and view all the answers

Which of the following calculations involves nuclear binding energy?

<p>$Q_{net} = M_{238}U - 8M_{4}He - M_{206}Pb$ (A)</p> Signup and view all the answers

What is the role of the factor $6.02 \times 10^{23}$ in nuclear decay calculations?

<p>Relates moles to number of nuclei (B)</p> Signup and view all the answers

What is the edge dimension of a 70.0-kg cube of uranium with a density of $18.7 × 10^3$ kg/m³?

<p>0.29 m (C)</p> Signup and view all the answers

Which of the following correctly describes the decay energy released in the decay of $^{238}U$?

<p>Decay energy can be calculated using the total mass defect. (A)</p> Signup and view all the answers

How is the power output ($ ext{℘}$) of a radioactive sample calculated?

<p>℘ = QR (D)</p> Signup and view all the answers

What is the decay constant ($ ext{λ}$) for $^{238}U$ given its half-life of $4.47 × 10^9$ years?

<p>$1.55 × 10^{-9}$ yr$^{-1}$ (A)</p> Signup and view all the answers

What type of decay does $^{238}U$ primarily undergo?

<p>Alpha decay (A)</p> Signup and view all the answers

In the context of applications of nuclear energy, which use is primarily associated with depleted uranium?

<p>Armor-piercing artillery (A)</p> Signup and view all the answers

If a radioactive material has a decay rate of $1.52 × 10^{18}$ counts per minute, what will its power output be if the decay energy is $Q$?

<p>Power output is determined by both decay rate and decay energy. (A)</p> Signup and view all the answers

How long would it take for a sample with a decay constant of $2.38 × 10^{-2}$ yr$^{-1}$ to decay to $1/10^{18}$ of its original amount?

<p>1.66 × 10^3 years (A)</p> Signup and view all the answers

Flashcards

Radiation Exposure Limit

Maximum permissible radiation absorption per year per kilogram of body mass.

Energy Absorption Rate

The rate at which energy from radiation is absorbed.

Nuclear Decay Chain Energy

The total energy released during a series of radioactive decays.

Decay Rate (R)

Number of radioactive decays per unit time

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Radioactive Decay Constant (λ)

Probability of a radioactive decay per unit time.

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Energy Released per Decay (Q)

Energy released in a single radioactive decay step.

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Power (P)

Rate of energy release in a radioactive decay process.

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Steady State Decay

When the rate of decay of a radioactive substance remains constant over time in sequences.

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Beta Particle Energy

The average kinetic energy of beta particles emitted by a radioactive source.

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Radioactive Decay Constant

The probability of a radioactive decay per unit of time.

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Number of Nuclei Remaining

The number of radioactive nuclei present after a certain time.

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Energy Released (Radioactive)

The total energy released during the decay process, considering the number of decays and energy per decay.

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Activity (Radioactive)

The rate of radioactive decay, measured in decays per unit time.

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Half-life (Radioactive)

The time it takes for half of the radioactive nuclei to decay.

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Initial Activity Calculation

Calculating activity from the decay constant and initial number of nuclei.

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Energy per decay

The energy released in a single radioactive decay event (usually given in keV).

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Uranium-238 decay edge dimension

The length of one side of a cube of uranium-238 with a given mass and density.

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Uranium-238 half-life

The time it takes for half of the uranium-238 atoms in a sample to decay.

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Uranium-238 decay chain

A series of radioactive decays starting with uranium-238 and ending with lead-206.

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Net decay energy (Qnet)

The total energy released during the entire uranium-238 decay chain.

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Radioactive power output

The rate at which a radioactive sample releases energy through decay.

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Depleted Uranium

Uranium-238 remaining after the enrichment process for uranium-235.

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Radioactive decay rate (R0)

The initial rate at which radioactive decays occur in a sample.

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Steady state decay (daughters)

State where the rate of decay is constant in a radioactive decay chain.

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Study Notes

Radioactive Decay Problems

  • Tritium Half-Life: Tritium (H) has a half-life of 12.33 years.
  • Tritium Age Measurement: Can be used to estimate the age of objects up to approximately 100 years. Produced in upper atmosphere; brought to Earth by rain.
  • Wine Age Estimation: Applying tritium decay, a bottle of wine with tritium levels similar to new wine's levels can have an estimated age close to 41 years.

Strontium-90

  • Nuclear Fission Product: Produced during nuclear fission of uranium (in reactors and bombs).
  • Chemical Similarity: Chemically similar to calcium, potentially dangerous if ingested, as body incorporates it into bones.
  • High Neutron Count: Has too many neutrons compared to other elements in the same periodic table column.
  • Half-Life: Strontium-90's half-life is about 29 years.
  • Decay Reaction: 90Sr → 90Y + e+
  • Daughter Nucleus Decay: The daughter nucleus, Y, is radioactive; 90Y undergoes further decay; a stable nucleus, 90Zr, is ultimately formed.
  • Time to Reach 1%: It will take approximately 193 years for the amount of 90Sr on Earth to reach 1% of its current level (assuming no new material is added).

Carbon-14 Dating

  • Constant Carbon-14: The amount of Carbon-14 in living organisms is assumed constant until the organism dies.
  • Decay after Death: After death, Carbon-14 decays, and the amount of Carbon-14 decreases over time.
  • Half-Life: The half-life of Carbon-14 is 5,730 years.
  • Age of Old Wooden Tool: If an old wooden tool contains only 6.0% of the Carbon-14 found in contemporary fresh wood, its estimated age is approximately 2.3 x 10⁴ years.

Radioactive Dating of a Dinosaur Bone

  • Initial Activity: The initial activity of the bone chip is calculated.
  • Time to 1% Level: It takes approximately 7500 years for the radioactivity level of a substance to decrease to 1% its initial activity.
  • Age Determination: Measuring the current activity of a bone sample allows us to estimate its age using a known half-life of carbon-14.
  • Conclusion: Given the estimated age of the bone sample in question and its age relative to the dinosaurs, it is improbable that the bone is that of a dinosaur.

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Description

This quiz covers concepts related to radioactive decay, focusing on tritium and strontium-90. Explore half-lives, age estimation of objects, and the chemical behavior of these isotopes. Test your understanding of nuclear fission products and their implications.

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