Structural isomerism in the alkanes

2 marks · Normal

State one difference and one similarity between structural isomers.

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Similarity: Structural isomers have the same molecular formula. Difference: Structural isomers have different structural formulae (different connections of atoms).

Also accept: Similarity: same number/types of atoms; Difference: different structure or shape

Common mistakes: Saying 'different numbers of atoms'; Saying 'same structure' instead of 'same formula'

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Marking points

B1 · 1 mark · States a correct similarity: same molecular formula (or same number of each atom).

B2 · 1 mark · States a correct difference: different structure/structural formula/connections.

Worked solution

Similarity: Structural isomers have the same molecular formula. Difference: Structural isomers have different structures or connectivity (structural formula).