R1.3 Energy from fuels questions
1. Wood is essentially composed of cellulose, hemicelluloses, and lignin. Different types of wood have
different calorific values but the average specific energy of wood is about 15 000 kJ kg−1. Good quality
anthracite contains about 95% carbon and 3% hydrogen by mass. The standard enthalpies of
combustion of carbon and hydrogen are − 394 and − 286 kJ mol−1 respectively.
i. Calculate the specific energy of good quality anthracite in kJ kg−1 (assuming that only the carbon
and hydrogen content of the anthracite undergoes combustion).
ii. Compare and contrast anthracite and wood as energy sources.
2. Pure octane has a density of 0.703 g cm−3. A typical car gasoline tank holds 55 dm3 of fuel. If a driver
uses one full tank of gasoline each week, calculate how much it contributes to his or her carbon
footprint in tonnes per year. (Assume that that the driver carries no passengers and that gasoline has
the same chemical and physical properties as pure octane).
3. Gasoline in some countries is labelled as E5 and E10. Assume E5 contains 5% ethanol and 95% octane,
whereas E10 contains 10% ethanol and 90% octane by volume .
i. Compare the energy provided by 1 dm3 of E10 to the energy provided by 1 dm3 of E5.
(Energy density of octane = 33600 kJ dm−3 ; energy density of ethanol = 23400 kJ dm−3)
ii. State two advantages of using E10 fuel rather than E5 fuel in cars that run on gasoline.
© Dr. Geoffrey Neuss, InThinking
https://www.thinkib.net/chemistry 1
1. Wood is essentially composed of cellulose, hemicelluloses, and lignin. Different types of wood have
different calorific values but the average specific energy of wood is about 15 000 kJ kg−1. Good quality
anthracite contains about 95% carbon and 3% hydrogen by mass. The standard enthalpies of
combustion of carbon and hydrogen are − 394 and − 286 kJ mol−1 respectively.
i. Calculate the specific energy of good quality anthracite in kJ kg−1 (assuming that only the carbon
and hydrogen content of the anthracite undergoes combustion).
ii. Compare and contrast anthracite and wood as energy sources.
2. Pure octane has a density of 0.703 g cm−3. A typical car gasoline tank holds 55 dm3 of fuel. If a driver
uses one full tank of gasoline each week, calculate how much it contributes to his or her carbon
footprint in tonnes per year. (Assume that that the driver carries no passengers and that gasoline has
the same chemical and physical properties as pure octane).
3. Gasoline in some countries is labelled as E5 and E10. Assume E5 contains 5% ethanol and 95% octane,
whereas E10 contains 10% ethanol and 90% octane by volume .
i. Compare the energy provided by 1 dm3 of E10 to the energy provided by 1 dm3 of E5.
(Energy density of octane = 33600 kJ dm−3 ; energy density of ethanol = 23400 kJ dm−3)
ii. State two advantages of using E10 fuel rather than E5 fuel in cars that run on gasoline.
© Dr. Geoffrey Neuss, InThinking
https://www.thinkib.net/chemistry 1
