Inthinking R1.3 Energy from fuels questions

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).

Respuesta: 35, 450 K]/kg

ii) Compare and contrast anthracite and wood as energy sources.

Respuesta: Anthracite has much larger specific energy than wood as twice as much. Anthracite is a coal , a fossilfuel. It is more dangerous to mine than growing and taking wood 0 . 95 (1000g) 394K] , 200K) Anthracite can\'t be replaced and contributes to global warming by releasing CO2 into the atmosphere wood is renewable fuel and it doesn\'t alter the amount of CO2 in the atmosphere.

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)

Respuesta: 6.2 tonnes / year

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)

Respuesta: 5/100x23400 = 1,170 95/100x33600 = 31,920 10/100x23400 = 2,340 90/100x33600 = 30,240 E10 will have small lower total energy content than E5 because ethanol has a low specific energy than octane. E5 provides slightly more energy than E10 due to its higher octane content

State two advantages of using E10 fuel rather than E5 fuel in cars that run on gasoline

Respuesta: 1. Reduces greenhouse gas emissions. Ethanol is renewable biofuel that can reduce a vehicle\'s carbon footprint. When it gets blended with gasoline, ethanol helps lower overall greenhouse gas emissions from the vehicle. 2. Enhanced engine performance, ethanol has higher octane rating than gasoline. Which can improve engine efficiency