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In many countries, ethanol is present in petrol as a renewable fuel additive to reduce dependence on fossil fuels - VCE - SSCE Chemistry - Question 7 - 2008 - Paper 1
Question 7
In many countries, ethanol is present in petrol as a renewable fuel additive to reduce dependence on fossil fuels. a. Write a chemical equation for the combustion o... show full transcript
Worked Solution & Example Answer:In many countries, ethanol is present in petrol as a renewable fuel additive to reduce dependence on fossil fuels - VCE - SSCE Chemistry - Question 7 - 2008 - Paper 1
Step 1
a. Write a chemical equation for the combustion of ethanol in excess oxygen.
Answer
The balanced chemical equation for the combustion of ethanol ( ext{C}_2 ext{H}_5 ext{OH}) in excess oxygen is:
ightarrow 2 ext{CO}_2 + 3 ext{H}_2 ext{O} $$ This equation shows that one mole of ethanol reacts with three moles of oxygen to produce two moles of carbon dioxide and three moles of water.Step 2
b. Give chemical reasons why ethanol can mix with both water and petrol.
Answer
Ethanol ( ext{C}_2 ext{H}_5 ext{OH}) is capable of mixing with water due to the presence of the polar hydroxyl ( ext{-OH}) group, which forms hydrogen bonds with water molecules. This interaction allows for a homogenous mixture.
In addition, ethanol has a non-polar hydrocarbon chain ( ext{-C}_2 ext{H}_5) which is similar to the non-polar molecules found in petrol (a mixture of hydrocarbons). This non-polar region enables ethanol to interact favorably with the components of petrol, making them miscible.
Step 3
c. i. Write a chemical equation for the fermentation of glucose to produce ethanol.
Answer
The chemical equation that represents the fermentation of glucose ( ext{C}6 ext{H}{12} ext{O}_6) to produce ethanol is:
ightarrow 2 ext{C}_2 ext{H}_5 ext{OH} + 2 ext{CO}_2 $$ This equation illustrates that one mole of glucose ferments to yield two moles of ethanol and two moles of carbon dioxide.Step 4
c. ii. Explain why ethanol produced by fermentation is referred to as a ‘biochemical fuel’.
Answer
Ethanol produced by fermentation is considered a ‘biochemical fuel’ because it is derived from biological processes involving living organisms, specifically yeast. The conversion of glucose into ethanol through fermentation is a metabolic process, showcasing how biological systems can produce energy-dense fuels. This contrasts with fossil fuels, which are formed from ancient biological matter over millions of years, but without biological processes being currently active. Thus, fermentation represents a renewable and sustainable method of producing fuel.