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Date May 2017 Marks available 1 Reference code 17M.3.sl.TZ2.12
Level SL Paper 3 Time zone TZ2
Command term State 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, 1 2 H , with tritium, 1 3 H , to form helium, 2 4 H e . 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

1 2 H 1 3 H  →  2 4 H e 0 1 n

 

Accept "n" for " 0 1 n "

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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Options » C: Energy
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