Chemistry · Grades 10–12
Carbon balance on combustion
In complete hydrocarbon combustion, each carbon atom contributes one CO₂ molecule. This is a paper stoichiometry model.
Rule and assumptions
In complete hydrocarbon combustion, each carbon atom contributes one CO₂ molecule. This is a paper stoichiometry model.
n(CO₂) = carbon count × n(hydrocarbon)
Worked examples
A hydrocarbon molecule contains 5 carbon atoms. In a complete-combustion model, all its carbon forms CO₂. How many moles of CO₂ come from 4.3 mol hydrocarbon? Round to 3 decimal places if needed. Answer in mol.
n(CO₂) = carbon count × n(hydrocarbon) 5 × 4.3 = 21.5
21.5 mol
A hydrocarbon molecule contains 7 carbon atoms. In a complete-combustion model, all its carbon forms CO₂. How many moles of CO₂ come from 7.4 mol hydrocarbon? Round to 3 decimal places if needed. Answer in mol.
n(CO₂) = carbon count × n(hydrocarbon) 7 × 7.4 = 51.8
51.8 mol
Try two questions
A hydrocarbon molecule contains 5 carbon atoms. In a complete-combustion model, all its carbon forms CO₂. How many moles of CO₂ come from 5.4 mol hydrocarbon? Round to 3 decimal places if needed. Answer in mol.
A hydrocarbon molecule contains 6 carbon atoms. In a complete-combustion model, all its carbon forms CO₂. How many moles of CO₂ come from 6.4 mol hydrocarbon? Round to 3 decimal places if needed. Answer in mol.
Answers and reasoning
Answers and marking notes
- 27 mol
n(CO₂) = carbon count × n(hydrocarbon) 5 × 5.4 = 27
- 38.4 mol
n(CO₂) = carbon count × n(hydrocarbon) 6 × 6.4 = 38.4
Further reading and review references
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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.