Question 23M.2.HL.TZ2.5
| Date | May 2023 | Marks available | [Maximum mark: 9] | Reference code | 23M.2.HL.TZ2.5 |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Compare, Identify, Outline | Question number | 5 | Adapted from | N/A |
When tritium () decays by beta-minus (β−) decay, one of the products is a stable isotope of helium (He).
Outline what is meant by an isotope.
[1]
«An atom with» the same number of protons AND different numbers of neutrons
OR
Same chemical properties AND different physical properties ✓
Do not allow just atomic number and mass number
Identify, for the helium isotope produced in the tritium decay, its
mass number.
[1]
3 ✓
proton number.
[1]
2 ✓
Outline the quark change that occurs during this decay.
[1]
d→u ✓
Compare the properties of the strong nuclear force and of the electromagnetic force that allow the helium nucleus to be stable.
[3]
Strong force is short range & electromagnetic force is long range ✓
Strong force is attractive between nucleons/neutrons & protons ✓
electromagnetic force is repulsive between protons ✓
Overall, the strong force dominates ✓
A beta-minus particle and an alpha particle have the same initial kinetic energy.
Outline why the beta-minus particle can travel further in air than the alpha particle.
[2]
Alphas have double charge «and so are better ionisers »✓
alphas have more mass and therefore slower «for same energy» ✓
so longer time/more likely to interact with the «atomic» electrons/atoms «and therefore better ionisers» ✓
Accept reverse argument in terms of betas travelling faster.