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Date May 2021 Marks available 1 Reference code 21M.2.SL.TZ1.5
Level Standard level Paper Paper 2 Time zone 1
Command term Outline Question number 5 Adapted from N/A

Question

Radioactive uranium-238 U92238 produces a series of decays ending with a stable nuclide of lead. The nuclides in the series decay by either alpha (α) or beta-minus (β) processes.

The graph shows the variation with the nucleon number A of the binding energy per nucleon.

Uranium-238 decays into a nuclide of thorium-234 (Th).


Write down the complete equation for this radioactive decay.

[1]
a.

Thallium-206 Tl81206 decays into lead-206 Pb82206.

Identify the quark changes for this decay.

 

[1]
b.

Outline why high temperatures are required for fusion to occur

 

[2]
c.i.

Outline, with reference to the graph, why energy is released both in fusion and in fission.

 

[1]
c.ii.

Uranium-235 (U92235) is used as a nuclear fuel. The fission of uranium-235 can produce krypton-89 and barium-144.

Determine, in MeV and using the graph, the energy released by this fission.

 

[2]
c.iii.

Markscheme

U→«92238»90234Th+«»24α ✓ 

Allow He for alpha.

a.

udd→uud
OR
down quark changes to up quark  

b.

links temperature to kinetic energy/speed of particles

energy required to overcome «Coulomb» electrostatic repulsion   

c.i.

«energy is released when» binding energy per nucleon increases

c.ii.

any use of (value from graph) x (number of nucleons) 

«235×7.6-89×8.6+144×8.2=» 160 «MeV»  

c.iii.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.
[N/A]
c.iii.

Syllabus sections

Core » Topic 7: Atomic, nuclear and particle physics » 7.2 – Nuclear reactions
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