Structural isomerism in the alkanes
3 marks · EasyState the molecular formula for hexane.
Explain what makes two different hexane molecules structural isomers.
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(a) C6H14
(b) They have the same molecular formula (C6H14) but different structural formulas—atoms joined in a different order (e.g., different arrangements of the carbon chain or branches).
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Marking points
B1 (a) · 1 mark · Correct formula for hexane: C6H14
M1 (b) · 1 mark · States that both have same molecular formula
A1 (b) · 1 mark · Explains they have different structures/connections (arrangement of atoms is different)
Worked solution
a) The molecular formula for hexane is C6H14.
b) Two different hexane molecules can be structural isomers because although they both have the formula C6H14, their atoms are joined in different ways (different carbon skeletons or branches).