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

Mass defect and nuclear binding energy — practice question

(a)[2]

State the meaning of nuclear binding energy.

(b(i))[1]

When uranium-235 ($^{235}_{92}\text{U}$) takes in a slow-moving neutron, one possible nuclear reaction is $^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{95}_{42}\text{Mo} + ^{139}_{57}\text{La} + 2^{1}_{0}\text{n} + 7^{0}_{-1}\beta + \text{energy}$. State the name of this kind of nuclear reaction.

(b(ii))[3]

On Fig. 8.1, show the position of 1. the uranium-235 nucleus (label this position U), 2. the molybdenum-95 ($^{95}_{42}\text{Mo}$) nucleus (label this position Mo), 3. the lanthanum-139 ($^{139}_{57}\text{La}$) nucleus (label this position La).

(b)

Fig. 8.1 shows the way the binding energy per nucleon $B_E$ varies with nucleon number $A$.

(b(iii))[5]

The masses of some particles and nuclei are given in Fig. 8.2. Calculate, for this reaction, 1. the change, in $\text{u}$, of the rest mass, 2. the energy released, in MeV, to three significant figures.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Energy needed to separate nucleons in a nucleus to infinity

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