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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 (C₂H₅OH) in excess oxygen (O₂) is:
ightarrow 2CO₂ + 3H₂O$$ This shows that one mole of ethanol reacts with three moles of oxygen to produce two moles of carbon dioxide and three moles of water.Step 2
b. Give chemical reasons why ethanol can mix with both water and petrol.
Answer
Ethanol is miscible with water due to the presence of its polar -OH group, which can form hydrogen bonds with water molecules. This polarity allows ethanol to interact favorably with the polar molecules of water,
On the other hand, ethanol is also miscible with petrol, a mixture of hydrocarbons, because its ethyl (-C₂H₅) group is non-polar. This non-polar character allows ethanol to interact with the non-polar hydrocarbons in petrol, leading to its miscibility.
Step 3
c. i. Write a chemical equation for the fermentation of glucose to produce ethanol.
Answer
The chemical equation for the fermentation of glucose (C₆H₁₂O₆) to produce ethanol (C₂H₅OH) is:
ightarrow 2C₂H₅OH + 2CO₂$$ This equation illustrates that one mole of glucose is converted into 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 termed a 'biochemical fuel' because its production involves biological processes using enzymes and microorganisms, typically yeast, to convert sugars into ethanol and carbon dioxide. This contrasts with traditional fuels, which are often derived from fossil sources without biological involvement. The term highlights the renewable aspect of biofuels, as they can be produced from biomass and agricultural resources.