Question 18N.3.hl.TZ0.12
| Date | November 2018 | Marks available | [Maximum mark: 9] | Reference code | 18N.3.hl.TZ0.12 |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Calculate, Deduce, Explain, Outline | Question number | 12 | Adapted from | N/A |
The Sun’s energy is produced by the fusion of hydrogen nuclei.
Explain fusion reactions with reference to binding energy.
[2]
small/lighter nuclei combine to form larger/heavier nuclei ✔
product has higher binding energy «per nucleon» ✔
Accept binding energy curve with explanation.
Uranium-238 produces plutonium-239, which is used as fuel in breeder reactors.
Outline why the term breeder is used for the reactors.
[1]
converts non-fissile «238U» material into fissile «239Pu» material
OR
produces more fissile material than it consumes ✔
Deduce the fission reaction when 239Pu is bombarded with a neutron to produce 133Xe and 103Zr.
[1]
239Pu + 1n → 133Xe + 103Zr + 41n ✔
Accept equation with correct atomic numbers included.
Accept notation for neutrons of “n”.
Accept a correctly described equation in words.
Nuclear disasters release radioactive caesium into the atmosphere, which presents serious health risks.
Cs-137 has a half-life of 30 years.
Calculate the percentage of Cs-137 remaining in the atmosphere after 240 years.
[2]
ALTERNATIVE 1:
«» 8 /8 half-lives «required» ✔
% remaining = «0.508 × 100 =» 0.39 «%» ✔
ALTERNATIVE 2:
λ = «» 0.023 ✔
% remaining = «100 × e–0.023 × 240 =» 0.39 «%» ✔
Award [2] for correct final answer.
Nuclear energy produces ionizing radiation which leads to the formation of free radicals.
Deduce a Lewis (electron dot) structure of the superoxide, O2–, free radical.
[1]
OR
Accept any combination of dots, crosses and lines to represent electrons.
Do not penalize missing brackets.
Penalize missing negative charge.
Explain why free radicals are harmful to living cells.
[2]
highly reactive
OR
start redox reactions ✔
damage/mutate DNA
OR
cause cancer
OR
damage enzymes ✔