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2017 O Level Chem P1 Q18 — Redox / Oxidation State Solution

Redox / Oxidation State 2017 O Level Pure Chemistry · Paper 1 · Q18

Question

Ethanol is oxidised to ethanoic acid by acidified potassium dichromate(VI). 3C₂H₅OH + 2K₂Cr₂O₇ + 8H₂SO₄ → 3CH₃CO₂H + 11H₂O + 2K₂SO₄ + 2Cr₂(SO₄)₃ What is the final oxidation state of chromium?

A+3
B+2
C−2
D−3

Correct answer: A

Video Solution

Explanation

Answer: A. In the product \(\text{Cr}_2(\text{SO}_4)_3\) each sulfate ion is \(-2\), giving \(-6\) overall, balanced by two chromium ions, so each chromium is +3.

The final oxidation state of chromium is +3.

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