One fusion reaction occurring in the sun is the fusion of deuterium, \({}_1^2H\), with tritium, \({}_1^3H\), to form helium, \({}_2^4He\). State a nuclear equation for this reaction.

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

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

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

\({}_1^2H\) + \({}_1^3H\) → \({}_2^4He\) + \({}_0^1n\)

Accept "n" for "\({}_0^1n\)"

Accept "²H + ³H → ⁴He + ¹n/n".

[1 mark]

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]

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]

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

[1 mark]