Ethanol as a Fuel

01Ethanol as a Fuel

Combustion of ethanol

This section covers the complete combustion of ethanol and the properties that affect its use as a fuel.

Complete combustion

When ethanol undergoes complete combustion in oxygen, it forms carbon dioxide and water.

$\ce{CH3CH2OH + 3O2 -> 2CO2 + 3H2O}$

Ethanol as a fuel

Ethanol can be used as a fuel. When it burns, its flame can be difficult to see because the flame is almost invisible.

Energy density

Ethanol has a lower energy density than gasoline. A vehicle using ethanol therefore needs more fuel to supply a given amount of energy, requiring a larger fuel supply or more frequent refuelling.

Blending ethanol with gasoline or diesel increases the energy density relative to pure ethanol. A blended fuel also produces a flame that is easier to see if a fire occurs.

Exam Tip: When balancing ethanol combustion, remember that the ethanol molecule already contains oxygen. Balance carbon and hydrogen first, then count the total oxygen atoms before choosing the coefficient for $\ce{O2}$ .

02Ethanol as a Fuel

Bioethanol and carbon neutrality

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Bioethanol

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Following the carbon dioxide

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$\ce{6CO2 + 6H2O -> C6H12O6 + 6O2}$

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$\ce{C6H12O6 -> 2CH3CH2OH + 2CO2}$

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$\ce{2CH3CH2OH + 6O2 -> 4CO2 + 6H2O}$

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Why bioethanol is not completely carbon neutral

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03Ethanol as a Fuel

Environmental and ethical issues

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Deciding whether to use bioethanol

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Consideration	Significance
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