Some chemical reactions of organic compounds
2 marks · EasyExplain why the reaction between ethene (C2H4) and bromine (Br2) is classified as an addition reaction.
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Must show: Describes 'addition' means something is added to a molecule, States nothing is removed from the original molecule
Also accept: Both Br atoms are added to the ethene molecule without removing any atoms
Common mistakes: Suggesting that hydrogen atoms are replaced; Calling it substitution
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Marking points
M1 · 1 mark · States that both atoms of bromine are added to ethene (no atoms are removed).
M2 · 1 mark · Explains that this fits the definition of an addition reaction.
Worked solution
In the reaction, both bromine atoms are added to the ethene molecule across the double bond. No atoms are lost from ethene or bromine, so this is an addition reaction by definition.