Write the balanced equation for the oxidation of ethanol to acetic acid using potassium dichromate in acidic medium. State the number of electrons transferred per mole of ethanol.

Step-by-step solution

1. Step 1: Write the oxidation half‑reaction for ethanol: $ceC2H5OH->CH3COOH+2H++2e-$ (2 e– are transferred per ethanol).
2. Step 2: Write the reduction half‑reaction for dichromate in acid: $ceCr2O{7}^{2-}+14H++6e-->2C{r}^{3+}+7H2O$ (6 e– are required).
3. Step 3: Balance electrons by multiplying ethanol half‑reaction by 3 and dichromate half‑reaction by 1: $3(ceC2H5OH->CH3COOH+2H++2e-)$ and $ceCr2O{7}^{2-}+14H++6e-->2C{r}^{3+}+7H2O$.
4. Step 4: Add the two half‑reactions and cancel common species (6e–, 14H+).
5. Step 5: Convert $ceC{r}^{3+}$ to $ceCr2O3$ by adding $ce2K2SO4$ and $ce2K2SO4$ as spectator ions in acidic medium.
6. Step 6: The final balanced equation is $ceC2H5OH+K2Cr2O7+4H2SO4->CH3COOH+Cr2O3+K2SO4+4H2O$.
7. Step 7: From the half‑reaction, 6 electrons are transferred per mole of ethanol.

Concept tested: Redox stoichiometry in acid medium

Published 5 September 2026 · How this solution was prepared and checked