Write the balanced equation for the oxidation of 1‑propanol (CH₃CH₂CH₂OH) to propionic acid (CH₃CH₂COOH) using potassium dichromate (K₂Cr₂O₇) in acidic medium. State the number of electrons transferred per mole of 1‑propanol and calculate the mass of propionic acid obtained from 5.0 g of 1‑propanol assuming quantitative conversion. (Molar mass 1‑propanol = 60.10 g mol⁻¹; propionic acid = 74.08 g mol⁻¹.)

Step-by-step solution

1. Half‑reaction for propanol oxidation: $ceCH3CH2CH2OH->CH3CH2COOH+2H++2e-$.
2. Half‑reaction for dichromate reduction: $ceCr2O{7}^{2-}+14H++6e-->2C{r}^{3+}+7H2O$.
3. Multiply propanol half by 3 to match 6 e-: $3ceCH3CH2CH2OH->3CH3CH2COOH+6H++6e-$.
4. Add the two half‑reactions and cancel electrons: $3ceCH3CH2CH2OH+Cr2O{7}^{2-}+14H+->3CH3CH2COOH+2C{r}^{3+}+7H2O$.
5. Electrons transferred per mole of propanol = 2 (from the oxidation half).
6. Moles of 1‑propanol: $\frac{5.0\text{ g}}{60.10{\text{ g mol}}^{-1}}=0.0833\text{ mol}$.
7. Mass of propionic acid: $0.0833\text{ mol}\times 74.08{\text{ g mol}}^{-1}=6.18\text{ g}$.
8. Thus 6.18 g of propionic acid is obtained.

Concept tested: Redox stoichiometry and electron count

Published 11 September 2026 · Last updated 16 September 2026 · How this solution was prepared and checked