CART Nuclear Chemistry and Radioactivity 2 — Questions and Answers
Question 1: Which conservation law requires that the mass numbers balance in a nuclear equation?
- Conservation of charge only
- Conservation of mass number and atomic number (Correct answer)
- Conservation of energy only
- Conservation of momentum only
Correct answer: Conservation of mass number and atomic number
In nuclear equations, both the total mass number (nucleons) and total atomic number (charge) must be equal on both sides of the equation.
Question 2: Nuclear fission is best described as:
- Two light nuclei combining to form a heavier nucleus
- A heavy nucleus splitting into two smaller nuclei (Correct answer)
- A nucleus emitting a gamma ray without changing mass
- A proton capturing an electron to form a neutron
Correct answer: A heavy nucleus splitting into two smaller nuclei
Nuclear fission involves the splitting of a heavy nucleus (like uranium-235) into two smaller nuclei, releasing a large amount of energy.
Question 3: Carbon-14 radioactive dating is useful for determining:
- The age of rocks formed from magma
- The age of organic (carbon-containing) materials up to ~50,000 years old (Correct answer)
- The purity of synthetic chemical compounds
- The energy content of fossil fuels
Correct answer: The age of organic (carbon-containing) materials up to ~50,000 years old
Carbon-14 (half-life ~5,730 years) is incorporated into living organisms; after death the C-14 decays, allowing age estimation up to about 50,000 years.
Question 4: Gamma radiation differs from alpha and beta radiation in that gamma radiation:
- Carries a positive charge
- Is composed of high-speed neutrons
- Is electromagnetic radiation with no mass or charge (Correct answer)
- Decreases the atomic number of the nucleus
Correct answer: Is electromagnetic radiation with no mass or charge
Gamma rays are high-frequency electromagnetic waves (photons) with no rest mass and no electric charge, unlike alpha (+2) and beta (−1) particles.
Question 5: In beta-minus decay, a neutron is converted inside the nucleus into:
- A proton and an emitted electron (beta particle) (Correct answer)
- An alpha particle and a gamma ray
- Two protons and a positron
- A proton and an emitted positron
Correct answer: A proton and an emitted electron (beta particle)
Beta-minus decay: n → p + e⁻ + antineutrino; the proton stays in the nucleus and the electron (beta particle) is emitted.
Question 6: What is a nuclear chain reaction?
- A series of chemical reactions that produce heat
- A process where neutrons from fission trigger additional fissions, releasing more neutrons (Correct answer)
- A sequence of alpha decays in a single isotope
- A reaction that requires a magnetic field to sustain
Correct answer: A process where neutrons from fission trigger additional fissions, releasing more neutrons
In a chain reaction, each fission event releases neutrons that cause further fissions, creating a self-sustaining cascade of reactions.
Question 7: Which isotope notation correctly represents an alpha particle?
- ₁⁰e
- ₂⁴He (Correct answer)
- ₁¹H
- ₀¹n
Correct answer: ₂⁴He
An alpha particle is written as ₂⁴He because it contains 2 protons (atomic number 2) and a mass number of 4 (2 protons + 2 neutrons).
CART Nuclear Chemistry and Radioactivity 2
Which conservation law requires that the mass numbers balance in a nuclear equation?