How many moles of dichromate ion will be required to oxidize one mole of $Fe^{2+}$ to $Fe^{3+}$ ions in acidic solution?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 1/6
The half-reactions in acidic solution are:
Oxidation:
$Fe^{2+} → Fe^{3+} + e^-$
Reduction:
${Cr_2O}_7^{2-} + 14 H^+ + 6 e^- → 2 Cr^{3+} + 7 H_2O$
- 1 dichromate ion (Cr₂O₇²⁻) accepts 6 electrons.
- 1 Fe²⁺ loses 1 electron.
So, moles of dichromate needed per mole of Fe²⁺:
$\frac{1}{6}$