Question 21N.2.SL.TZ0.5
| Date | November 2021 | Marks available | [Maximum mark: 9] | Reference code | 21N.2.SL.TZ0.5 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate, Draw, Identify, Show that, State | Question number | 5 | Adapted from | N/A |
State what is meant by the binding energy of a nucleus.
[1]
the energy needed to «completely» separate the nucleons of a nucleus
OR
the energy released when a nucleus is assembled from its constituent nucleons ✓
Accept reference to protons AND neutrons.
Draw, on the axes, a graph to show the variation with nucleon number of the binding energy per nucleon, . Numbers are not required on the vertical axis.
[2]
curve rising to a maximum between 50 and 100 ✓
curve continued and decreasing ✓
Ignore starting point.
Ignore maximum at alpha particle
Identify, with a cross, on the graph in (a)(ii), the region of greatest stability.
[1]
At a point on the peak of their graph ✓
Plutonium-238 (Pu) decays by alpha (α) decay into uranium (U).
The following data are available for binding energies per nucleon:
plutonium 7.568 MeV
uranium 7.600 MeV
alpha particle 7.074 MeV
Show that the energy released in this decay is about 6 MeV.
[3]
correct mass numbers for uranium (234) and alpha (4) ✓
«MeV» ✓
energy released 5.51 «MeV» ✓
Ignore any negative sign.
The plutonium nucleus is at rest when it decays.
Calculate the ratio .
[2]
«» OR ✓
«» ✓
Award [2] marks for a bald correct answer.
Accept for MP2.