Alkanes
2 marks · EasyExplain why the reaction between propane and chlorine in ultraviolet light is called a substitution reaction. Use a chemical equation to support your answer.
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Must show: States that a hydrogen atom is replaced by a chlorine atom, Chemical equation showing substitution, Mentions UV light if possible
Common mistakes: Describing an addition rather than substitution; Omitting that a hydrogen is replaced by chlorine
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Marking points
M1 · 1 mark · States that a hydrogen atom in propane is replaced by (substituted with) a chlorine atom.
A1 · 1 mark · Writes a correct chemical equation for the mono-substitution: (or equivalent displayed).
Worked solution
In a substitution reaction, one atom is replaced by another. Here, a hydrogen atom in propane is replaced by a chlorine atom when propane reacts with chlorine under ultraviolet light.
This shows that one hydrogen in propane is swapped for a chlorine, making chloropropane and hydrogen chloride.