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Date May 2017 Marks available 2 Reference code 17M.3.sl.TZ2.12
Level SL Paper 3 Time zone TZ2
Command term Explain Question number 12 Adapted from N/A

Question

The sun is the main source of energy used on earth.

One fusion reaction occurring in the sun is the fusion of deuterium, 21H, with tritium, 31H, to form helium, 42He. State a nuclear equation for this reaction.

[1]
a.i.

Explain why this fusion reaction releases energy by using section 36 of the data booklet.

[2]
a.ii.

State the technique used to show that the sun is mainly composed of hydrogen and helium.

[1]
a.iii.

Coloured molecules absorb sunlight. Identify the bonding characteristics of such molecules.

[1]
b.

Markscheme

21H31H → 42He10n

 

Accept "n" for "10n"

Accept "2H + 3H → 4He + 1n/n".

[1 mark]

a.i.

higher binding energy/BE «per nucleon» for helium/products
OR
nucleons in products more tightly bound

mass defect/lost matter converted to energy

 

Accept converse statement in M1.

Accept “mass deficit” for “mass defect”.

[2 marks]

a.ii.

spectrometry

 

Accept “spectroscopy” for “spectrometry” OR more specific techniques such as “atomic absorption spectrometry/AAS”, “astrophotometry” etc. Do not award mark for incorrect specific spectrometric techniques.

Do not accept “spectrum”.

[1 mark]

a.iii.

«extensive system of» conjugation/alternating single and double «carbon to carbon» bonds
OR
delocalized electrons «over much of the molecule»

[1 mark]

b.

Examiners report

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

Syllabus sections

Options » C: Energy » C.3 Nuclear fusion and fission

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