DP Chemistry (last assessment 2024)

Test builder »

Question 18N.3.sl.TZ0.9

Select a Test
Date November 2018 Marks available [Maximum mark: 6] Reference code 18N.3.sl.TZ0.9
Level sl Paper 3 Time zone TZ0
Command term Calculate, Deduce, Explain, Outline Question number 9 Adapted from N/A
9.
[Maximum mark: 6]
18N.3.sl.TZ0.9

The Sun’s energy is produced by the fusion of hydrogen nuclei.

(a)

Explain fusion reactions with reference to binding energy.

[2]

Markscheme

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.

(b.i)

Outline why the term breeder is used for the reactors.

[1]

Markscheme

converts non-fissile «238U» material into fissile «239Pu» material

OR

produces more fissile material than it consumes ✔

(b.ii)

Deduce the fission reaction when 239Pu is bombarded with a neutron to produce 133Xe and 103Zr.

[1]

Markscheme

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.

(c)

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]

Markscheme

ALTERNATIVE 1:

« 240 30 = » 8 t 1 2 /8 half-lives «required» ✔

% remaining = «0.508 × 100 =» 0.39 «%» ✔

 

ALTERNATIVE 2:

λ = « 0.693 30 = » 0.023 ✔

% remaining = «100 × e–0.023 × 240 =» 0.39 «%» ✔

 

Award [2] for correct final answer.

Syllabus sections