Question 19M.2.SL.TZ2.6
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.2.SL.TZ2.6 |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Determine, Identify, Suggest | Question number | 6 | Adapted from | N/A |
Deuterium, , undergoes fusion according to the following reaction.
Identify particle X.
[1]
proton / / p ✔
At HL this was well answered with the most common wrong answer being ‘neutron’. At SL however, this was surprisingly wrongly answered by many. Suggestions given included most smallish particles, alpha, positron, beta, antineutrino and even helium.
The following data are available for binding energies per nucleon.
Determine, in MeV, the energy released.
[2]
«3 x 2.78 − 2 × 2 × 1.12»
See 3 × 2.78/8.34 OR 2 × 2 × 1.12/4.48✔
3.86 «MeV» ✔
The majority of candidates missed the fact that the figures given were the binding energies per nucleon. Many complicated calculations were also seen, particularly at SL, that involved E = mc2.
Suggest why, for the fusion reaction above to take place, the temperature of deuterium must be very high.
[2]
the deuterium nuclei are positively charged/repel ✔
high KE/energy is required to overcome «Coulomb/electrostatic» repulsion /potential barrier
OR
high KE/energy is required to bring the nuclei within range of the strong nuclear force ✔
high temperatures are required to give high KEs/energies ✔
The most common mark to be awarded here was the one for linking high temperature to high KE. A large number of candidates talked about having to overcome the strong nuclear force before fusion could happen.
Particle Y is produced in the collision of a proton with a K- in the following reaction.
The quark content of some of the particles involved are
Identify, for particle Y, the charge.
[1]
−1 / -e ✔
At SL many answers of just ‘negative’ were seen.
Identify, for particle Y, the strangeness.
[1]
−3 ✔
This was poorly answered at both levels with the most common answer being zero.