Ethanol can be oxidised by heating with potassium dichromate(VI) in dilute sulfuric acid
3 marks · NormalA student plans to oxidise ethanol using potassium dichromate(VI) in dilute sulfuric acid. Explain, with reasoning, the role of the sulfuric acid in this reaction and what would happen if it was not included.
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Sulfuric acid provides H+ ions, making potassium dichromate(VI) act as an oxidising agent. Without sulfuric acid, there are no H+ ions, so no redox reaction occurs and ethanol is not oxidised.
Also accept: Sulfuric acid acts as a source of hydrogen ions needed for the oxidising agent to work.; No ethanoic acid will be formed if sulfuric acid is not present.
Common mistakes: Believing sulfuric acid is the oxidising agent itself; Omitting role of H+ ions
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Marking points
M1 · 1 mark · States that sulfuric acid provides H+ ions.
M2 · 1 mark · Explains that the H+ ions allow potassium dichromate(VI) to oxidise ethanol.
A1 · 1 mark · States that no reaction or oxidation will occur if sulfuric acid is missing.
Worked solution
Sulfuric acid provides hydrogen ions (H+) which are essential for the potassium dichromate(VI) to function as an oxidising agent. The H+ ions allow the redox reaction to occur, so ethanol can be oxidised. If sulfuric acid is not included, there are no H+ ions. Therefore, potassium dichromate(VI) will not oxidise ethanol, and no reaction will take place.