Physical properties

3 marks · Normal

An alkene molecule contains 14 hydrogen atoms. Calculate the number of carbon atoms it contains. Show your working.

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7 (±0)

Common mistakes: Divide by 2n+2 instead of 2n; Incorrect arithmetic

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Marking points

M1 · 1 mark · Equate H = 2n using general formula (follow-through)

M2 · 1 mark · Rearrange correctly for n: n = H/2 (follow-through)

A1 · 1 mark · Correct answer n=7

Worked solution

The general formula is CnH2n.

So, the alkene has 7 carbon atoms.