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

Mass defect and nuclear binding energy — practice question

(a)[2]

Define the term mass defect.

(b)

Table 9.1 gives the mass defects for three nuclei. The fusion reaction in a certain star is given by $^{2}_{1}\text{H} + ^{3}_{1}\text{H} \rightarrow ^{4}_{2}\text{He} + X$ where $X$ is a particle that has no mass defect.

(b(i))[1]

State the identity of particle $X$.

(b(ii))[3]

Show that the energy released when one $^{4}_{2}\text{He}$ nucleus is produced in this fusion reaction is $2.8 \times 10^{-12}\ \text{J}$.

(c(i))[3]

The star in (b) has radius $2.3 \times 10^{9}\ \text{m}$ and luminosity $1.4 \times 10^{28}\ \text{W}$. Every bit of the energy released when $^{4}_{2}\text{He}$ forms is emitted from the star. All radiation from the star comes from the formation of $^{4}_{2}\text{He}$. Determine the mass of $^{4}_{2}\text{He}$ produced each second by the fusion process.

(c(ii))[2]

Determine the star’s surface temperature.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: difference in mass between the nucleus and the total mass of its nucleons

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