Problem: 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 VCH3COOH (aq) + 4 H3O+ (aq) + 4 e- → CH3CH2OH (aq) + 5 H2O (l)         ε°red = ???   acetic acid                                                 ethanolUsing the (appropriate) information below, calculate the overall potential for the fuel cell (Δε°) at 25 °C. Please circle your answer.

FREE Expert Solution

We are asked to calculate the overall potential for the fuel cell (ε°) at 25 °C.

Recall: 

 ΔG = -nFε°

where:

n = number of moles electrons

F = Faraday’s constant, 96485 C/mol e- 

ε° = standard reduction potential


We can use the following equation to solve for ΔG˚rxn:


ΔG°rxn=ΔG°f, prod-ΔG°f, react


We go through the following steps to solve the problem: 

Step 1: Write the overall chemical reaction

Step 2: Calculate  ΔG°rxn.

Step 3: Calculate the overall potential for the fuel cell 


Step 1: Write the overall chemical reaction

Recall the mnemonics LEO GER.

Lose               Gain

Electron         Electrons

Oxidation       Reduction


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Problem Details

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

Using the (appropriate) information below, calculate the overall potential for the fuel cell (Δε°) at 25 °C. Please circle your answer.

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