Ethanol can be oxidised by heating with potassium dichromate(VI) in dilute sulfuric acid
2 marks · EasyThe oxidation of ethanol with potassium dichromate(VI) requires dilute sulfuric acid.
A chemist accidentally forgets to add any dilute sulfuric acid to the test-tube, while potassium dichromate(VI) and ethanol are both present.
Calculate the number of moles of H+ ions available to the reaction in this mistake, assuming none are present in the other reagents.
Show your working and state the reason for your answer.
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Zero moles of H+ ions; because no sulfuric acid was added, there are no H+ ions available for the reaction. mol (±0)
Also accept: 0 (mol); no H+ ions; Zero; no H+ ions available; None; because sulfuric acid was not added
Common mistakes: Assuming H+ ions are present from potassium dichromate(VI) or ethanol; Giving a nonzero value for H+ ions
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Marking points
M1 · 1 mark · States or calculates that the number of moles of H+ ions is zero when no sulfuric acid is added.
A1 · 1 mark · Clearly explains the reason (no sulfuric acid means no source of H+ ions for the reaction).
Worked solution
Since the chemist did not add any dilute sulfuric acid, there is no source of H+ ions in the mixture.
Therefore, the number of moles of H+ ions present in the test-tube is 0 mol.
No H+ ions means the oxidation reaction cannot proceed.