An illustration of an ethanol fuel cell is given b...

Question

An illustration of an ethanol fuel cell is given below:

The half reactions (written as reductions) for the fuel cell at 25 °C are given below.

O₂ (g) + 4 H₃O⁺ (aq) + 4 e^- → 6 H₂O (l) ε°_red = 1.23 V

CH₃COOH (aq) + 4 H₃O⁺ (aq) + 4 e^- → CH₃CH₂OH (aq) + 5 H₂O (l) ε°_red = ???

acetic acid ethanol

Write the overall chemical reaction for the fuel cell, and list the product(s) released from the cell.

Jules Bruno · Accepted Answer

We’re being asked to write the overall chemical reaction for the fuel cell, and list the product(s) released from the cell.Recall the mnemonics LEO GER.Lose               GainElectron         ElectronsOxidation       Reduction[readmore]The ease to remove an electron from an element is also related to cell potential.• Lost electrons → oxidation → anode• Gained electrons  → reduction → cathodeGiven:O2 (g) + 4 H3O+ (aq) + 4 e- → 6 H2O (l)                                                        ε°red = 1.23 VCH3COOH (aq) + 4 H3O+ (aq) + 4 e- → CH3CH2OH (aq) + 5 H2O (l)           ε°red = ???We can see from the illustration that the electrons flow from the side of CH3COOH to the side of O2.CH3COOH (aq) → Lost electrons → oxidation → anodeO2 (g) → Gained electrons  → reduction → cathodeSince CH3COOH (aq) is oxidized we have to reverse the reaction when we combine: Also, note that there are already 4 e-  on both reactions so no need to modify further. Cathode: O2 (g) + 4 H3O+ (aq) + 4 e- → 6 1 H2O (l)                                                        Anode:    CH3CH2OH (aq) + 5 H2O (l)  → CH3COOH (aq) + 4 H3O+ (aq) +4 e-  _________________________________________________________________            O2 (g) + CH3CH2OH (aq) →  CH3COOH (aq) + H2O (l)  The overall chemical reaction for the fuel cell is: O2 (g) + CH3CH2OH (aq) →  CH3COOH (aq) + H2O (l)

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