Worksheet: Fusion Reactions in Stars

In this worksheet, we will practice determining the products of fusion reactions and identifying decay processes by their decay products.

Q1:

In the P–P III branch of the proton–proton chain reaction, a boron-8 nucleus becomes a beryllium-8 nucleus, releasing a positron and an electron neutrino in the process. This is shown in the following nuclear equation.

8584+eBBe+e+𝜈

What is the name of this process?

  • A𝛼 decay
  • BElectron capture
  • CPair production
  • D𝛽 decay
  • E𝛽 decay

Q2:

In the P–P II branch of the proton–proton chain reaction, a beryllium-7 nucleus and an electron combine to produce a lithium-7 nucleus and an electron neutrino. This is shown in the following nuclear equation.

7473eBe+eLi+𝜈

What is the name of this process?

  • ABeta decay
  • BInverse beta decay
  • CPair production
  • DAlpha decay
  • EElectron capture

Q3:

The following set of nuclear equations shows one way that helium-4 can be produced through the proton–proton fusion chain.

2HHe1122

2221+eHeD+e+𝜈

211132D+HHe+𝛾

2HeHe+2H324211

How many protons are needed in total to produce one helium-4 nucleus using this chain reaction only?

Q4:

The diagram shows six combinations of protons and neutrons.

Which of the following combinations is stable?

  • AThe tritium nucleus, the helium-3 nucleus, the deuterium nucleus, and the proton
  • BThe proton, the deuterium nucleus, the helium-3 nucleus, and the helium-4 nucleus
  • CThe tritium nucleus, the diproton, the helium-3 nucleus, and the helium-4 nucleus
  • DThe diproton, the deuterium nucleus, the helium-4 nucleus, and the tritium nucleus
  • EThe proton, the helium-4 nucleus, the diproton, and the tritium nucleus

Which of the following combinations is unstable?

  • AThe diproton and the tritium nucleus
  • BThe diproton and the helium-4 nucleus
  • CThe helium-3 nucleus and the proton
  • DThe deuterium nucleus and the helium-4 nucleus
  • ETritium nucleus and the helium-3 nucleus

Which of the following has the shortest half-life?

  • AThe proton
  • BThe helium-3 nucleus
  • CThe tritium nucleus
  • DThe deuterium nucleus
  • EThe diproton

Q5:

The diagram shows four combinations of protons and neutrons, where some form stable bound states, some form unstable bound states, and some cannot form bound states. Protons are represented by red circles and neutrons are represented by gray circles.

Which of the four combinations forms a bound state that is stable?

  • AThe trineutron
  • BThe helium-3 nucleus
  • CThe tritium nucleus
  • DThe triproton

Which of the four combinations forms a bound state that is unstable?

  • AThe triproton
  • BThe trineutron
  • CThe tritium nucleus
  • DThe helium-3 nucleus

Which of the four combinations cannot form bound states of particles?

  • AThe helium-3 nucleus
  • BThe tritium nucleus and the trineutron
  • CThe triproton and the helium-3 nucleus
  • DThe triproton and the trineutron
  • EThe tritium nucleus and the triproton

Q6:

In the first part of the proton–proton fusion chain, two protons must fuse together to form a diproton, as shown in the diagram.

What repulsive force acts between the two particles within the diproton?

  • AGravity
  • BThe weak nuclear force
  • CThe strong nuclear force
  • DElectrostatic repulsion

What non-negligible attractive force acts between the two particles within the diproton?

  • AThe weak nuclear force
  • BElectrostatic attraction
  • CThe strong nuclear force
  • DGravity

Q7:

In the first part of the proton–proton fusion chain, two protons fuse to form a bound state called a diproton. Diprotons, however, are unstable. The diagram shows one way in which diprotons can decay, producing a deuterium nucleus, a positron, and an electron neutrino. What name is given to this type of decay?

  • AElectron capture
  • B𝛽 decay
  • C𝛽 decay
  • DAlpha decay
  • ENuclear fission

Q8:

The diagram shows three pairs of protons and neutrons, where one forms a stable bound state, one forms an unstable bound state, and one does not form a bound state. Protons are represented by red circles and neutrons are represented by gray circles.

Which of the three pairs forms a bound state that is stable?

  • AThe dineutron
  • BThe deuterium nucleus
  • CThe diproton

Which of the three pairs forms a bound state that is unstable?

  • AThe dineutron
  • BThe deuterium nucleus
  • CThe diproton

Which of the three pairs does not form a bound state?

  • AThe diproton
  • BThe dineutron
  • CThe deuterium nucleus

Q9:

The following set of nuclear equations shows the P–P II branch of the proton–proton chain reaction.

3242He+HeBe+𝛾

Be+eX+e𝜈

X+p2He42

What is the value of 𝑞?

  • A1
  • B2
  • C5
  • D7
  • E4

What is the value of 𝑠?

  • A4
  • B7
  • C8
  • D6
  • E1

What is the missing particle 𝑋?

  • AA beryllium-7 nucleus
  • BA helium-3 nucleus
  • CA lithium-7 nucleus
  • DA lithium-8 nucleus
  • EA helium-4 nucleus

Q10:

The following set of nuclear equations shows the first part of the proton–proton chain reaction, in which two protons fuse to become a helium-2 nucleus, which is also known as a diproton, and then the helium-2 nucleus decays to become a deuterium nucleus. 111122H+HHe2221HeD+X+Y What are the particles X and Y that are produced in this reaction?

  • AA positron and an electron antineutrino
  • BAn electron and an electron neutrino
  • CA positron and an electron neutrino
  • DAn electron and an electron antineutrino

Q11:

The following nuclear equation shows the P-P I branch of the proton-proton chain reaction, in which two helium-3 nuclei are fused to produce a helium-4 nucleus. 2HeHe+2X3242 What is the particle X that is produced in this reaction?

  • AA hydrogen nucleus
  • BA deuterium nucleus
  • CA neutron
  • DAn electron

Q12:

The following nuclear equation shows the second part of the proton-proton chain reaction, which produces helium-3. X+YHe+32𝛾 What are the particles X and Y that must fuse in this reaction?

  • AA tritium nucleus and a proton
  • BA deuterium nucleus and a neutron
  • CA deuterium nucleus and a proton
  • DA tritium nucleus and a neutron

Q13:

The following set of nuclear equations shows the P-P III branch of the proton-proton chain reaction.

324274He+HeBe+𝛾

741185Be+HB+𝛾

85+BBe+e+X

Be2He42

What is the value of 𝑞?

What is the value of 𝑠?

What is the missing particle X?

  • AA positron
  • BAn electron
  • CA neutron
  • DAn electron antineutrino
  • EAn electron neutrino

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