Chemical reactions of the alkenes
3 marks · NormalAn alkene has 8 carbon atoms in its molecule.
Calculate the number of hydrogen atoms present in one molecule of this alkene. Show your working.
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16 (±0)
Common mistakes: Using alkane formula (CnH2n+2 instead of CnH2n); Calculating atomic mass rather than number of atoms
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Marking points
M1 · 1 mark · States or uses the correct general formula for alkenes: CnH2n.
M2 · 1 mark · Substitutes n = 8 correctly: H = 2 × 8.
A1 · 1 mark · Gives the correct number of hydrogen atoms: 16.
Worked solution
The general formula for alkenes is CnH2n.
There are 16 hydrogen atoms in a molecule of the alkene.