Ethanol can be oxidised by heating with potassium dichromate(VI) in dilute sulfuric acid
3 marks · NormalExplain, using your knowledge of acids and oxidation reactions, why dilute sulfuric acid is needed for potassium dichromate(VI) to oxidise ethanol.
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Dilute sulfuric acid provides H+ ions, which are necessary for the oxidising action of potassium dichromate(VI). Without these ions, the oxidation of ethanol does not occur.
Also accept: Dilute sulfuric acid supplies hydrogen ions needed for the redox reaction.; Potassium dichromate(VI) only works as an oxidising agent in acidic conditions.
Common mistakes: Only mentions acid as a catalyst without explaining role of H+.; States acid is needed but gives no reason.
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Marking points
M1 · 1 mark · Mentions sulfuric acid provides H+ (hydrogen) ions.
M2 · 1 mark · States redox/oxidation of ethanol requires these ions.
A1 · 1 mark · States without acid (or H+), oxidation will not occur.
Worked solution
Dilute sulfuric acid supplies H+ ions needed for the potassium dichromate(VI) to oxidise ethanol. The acid makes the solution acidic, which allows the oxidising agent to work. Without dilute sulfuric acid to provide H+ ions, no redox reaction occurs.