Date | November 2019 | Marks available | 3 | Reference code | 19N.2.SL.TZ0.7 |
Level | Standard level | Paper | Paper 2 | Time zone | 0 - no time zone |
Command term | Calculate | Question number | 7 | Adapted from | N/A |
Question
A stationary nucleus of uranium-238 undergoes alpha decay to form thorium-234.
The following data are available.
Energy released in decay 4.27 MeV
Binding energy per nucleon for helium 7.07 MeV
Binding energy per nucleon for thorium 7.60 MeV
Radioactive decay is said to be “random” and “spontaneous”. Outline what is meant by each of these terms.
Random:
Spontaneous:
Calculate the binding energy per nucleon for uranium-238.
Calculate the ratio .
Markscheme
random:
it cannot be predicted which nucleus will decay
OR
it cannot be predicted when a nucleus will decay ✔
NOTE: OWTTE
spontaneous:
the decay cannot be influenced/modified in any way ✔
NOTE: OWTTE
234 × 7.6 OR 4 × 7.07 ✔
BEU =« 234 × 7.6 + 4 × 7.07 – 4.27 =» « MeV » ✔
« MeV » ✔
NOTE: Allow ECF from MP2
Award [3] for bald correct answer
Allow conversion to J, final answer is 1.2 × 10–12
states or applies conservation of momentum ✔
ratio is «» 58.5 ✔
NOTE: Award [2] for bald correct answer