Question

The automobile fuel called E85 consists of 85% ethanol and 15% gasoline. E85 can be used in so-called flex-fuel vehicles (FFVs), which can use gasoline, ethanol, or a mix as fuels. Assume that gasoline consists of a mixture of octanes (different isomers of C8H18), that the average heat of combustion of C8H18(l) is 5400 kJ/mol, and that gasoline has an average density of 0.70 g/mL. The density of ethanol is 0.79 g/mL.

Part A: By using the information given, calculate the energy produced by combustion of 1.5 L of gasoline.

Part B: By using the information given as well as data in Appendix C, calculate the energy produced by combustion of 1.5 L of ethanol. Consider that water is in the gaseous state.

Answer 1

Part A: By using the information given, calculate the energy produced by combustion of 1.5 L of gasoline.

Given that; the automobile fuel called E85 consists of 85% ethanol and 15% gasoline

Here the volume of the automobile fuel = 1.5 L

Volume of gasoline

1.5L *85%= 1.5*85/100= 1.275 L

And density = mass / volume

Mass = volume * density

= 1.275 L*1000 ml/1.0L*0.70 g/ml

= 892.5 g

Now moles of gasoline = amount in g / molar mass

= 892.5 g/ 114 g/ mole

= 7.829 mole

Here that the average heat of combustion of C8H18(l) is 5400 kJ/mol

Then total heat = 7.829 mole *5400 kJ/mol

= 42276.32 KJ/ mol

= 4.23*10^4 KJ/ mol

Part B: By using the information given as well as data in Appendix C, calculate the energy produced by combustion of 1.5 L of ethanol. Consider that water is in the gaseous state.

Given that; the automobile fuel called E85 consists of 85% ethanol and 15% gasoline

Here the volume of the automobile fuel = 1.5 L

Volume of ethanol

1.5L *15%= 1.5*85/100= 0..225 L

And density = mass / volume

Mass = volume * density

= 0.225 L*1000 ml/1.0L*0.79 g/ml

= 177.75 g

Now moles of ethanol = amount in g / molar mass

= 177.75 g/ 46 g/ mole

= 3.86 mole ethanol

Here that the average heat of combustion of ethanol is 1370 kJ/mol

Then total heat by ethanol = 3.86 mole *1370 kJ/mol

= 5293.86 KJ/ mol

= 5.29*10^3 KJ/ mol