Your task is to determine E° for the reduction of CO₂(g) to C₃H₈(g) in two different ways and to explain why each gives the same result. 

(a) Consider a fuel cell in which the cell reaction corresponds to the complete combustion of propane gas. Write the half-cell reactions and the overall reaction. Determine Δ_rG° and E°_cell for the reaction, then obtain E°_CO2/_C3H8. 

(b) Without considering the oxidation that occurs simultaneously, obtain E°_CO2/_C3H8 directly from tabulated thermodynamic data for the reduction half-cell reaction.