Ethanol can be oxidised by heating with potassium dichromate(VI) in dilute sulfuric acid
2 marks · EasyA student observes the colour change when ethanol is heated with potassium dichromate(VI) in dilute sulfuric acid. Explain why the green colour appears during this reaction.
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The green colour appears because potassium dichromate(VI) is reduced to chromium(III) ions (Cr^{3+}) during the oxidation of ethanol.
Must show: reduction of dichromate(VI), formation of Cr^{3+} ions, link to green colour
Also accept: Green colour indicates Cr3+ ions are formed.; Potassium dichromate(VI) is reduced, causing a colour change to green due to chromium(III) ions.
Common mistakes: Ethanol turns green.; It is due to ethanoic acid.
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Marking points
M1 · 1 mark · Mentions that potassium dichromate(VI) is reduced when ethanol is oxidised.
A1 · 1 mark · Explains that the green colour is due to chromium(III) ions (Cr3+).
Worked solution
During the reaction, potassium dichromate(VI) is reduced as it oxidises ethanol.
This reduction produces chromium(III) ions (Cr^{3+}), which make the solution green.