DP Chemistry (last assessment 2024)

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Question 18M.3.sl.TZ1.12

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Date May 2018 Marks available [Maximum mark: 5] Reference code 18M.3.sl.TZ1.12
Level sl Paper 3 Time zone TZ1
Command term Explain, Suggest Question number 12 Adapted from N/A
12.
[Maximum mark: 5]
18M.3.sl.TZ1.12

Nuclear fission of 235U is one source of electrical energy that has a minimal carbon footprint.

(a.i)

Natural uranium needs to be enriched to increase the proportion of 235U. Suggest a technique that would determine the relative abundances of 235U and 238U.

[1]

Markscheme

mass spectrometry/mass spectroscopy/MS

 

Accept “analysis of radiation emitted”.

[1 mark]

(a.ii)

Explain how 235U fission results in a chain reaction, including the concept of critical mass.

[3]

Markscheme

critical mass: mass required so that «on average» each fission/reaction results in a further fission/reaction

Any two for [2 max]:

neutron captured by «235U» nucleus

fission/reaction produces many neutrons/more than one neutron

if these cause further fission/reaction a chain reaction occurs

 

Accept “minimum mass of fuel needed for the reaction to be self-sustaining”.

Accept answers in the form of suitable diagrams/equations.

[3 marks]

(b)

Suggest one reason why there is opposition to the increased use of nuclear fission reactors.

[1]

Markscheme

produce long lived/long half-life radioisotopes/radioactivity

OR

could be used to produce nuclear weapons

OR

«nuclear» accidents/meltdowns can occur

 

Accept “long lived/long half-life radioactive waste”.

[1 mark]

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