Physics 9702 · AS & A Level · Mass defect and nuclear binding energy

Mass defect and nuclear binding energy — practice question

(a)[2]

Define the binding energy of a nucleus.

(b(i))[1]

A uranium-238 nucleus at rest, $^{238}_{92}\text{U}$, decays to produce a thorium-234 nucleus, $^{234}_{90}\text{Th}$. An $\alpha$-particle and a gamma-ray photon are emitted. The decay is written as $^{238}_{92}\text{U} \rightarrow {}^{234}_{90}\text{Th} + {}^{4}_{2}\text{He} + {}^{0}_{0}\gamma$. State the connection between the binding energies of the nuclei that is consistent with this reaction being energetically possible.

(b(ii).1)[1]

Calculate, for this reaction, the change, in $\text{u}$, in mass.

(b(ii).2)[2]

Calculate, for this reaction, the total energy released, in $\text{J}$.

(b(ii)(1))[1]

Calculate, for this reaction, the change, in $\text{u}$, of the mass.

(b(ii)(2))[2]

Calculate, for this reaction, the total energy released, in J.

(b(iii))[2]

State and explain whether the energy of the gamma-ray photon is equal to the energy released in the reaction.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: minimum energy / work needed to separate nucleons to infinity

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