We’re being asked to determine the Gibbs free energy at 2500 °C for the given reaction:
C2H5OH(l) + 3 O2(g)→ 2 CO2(g) + 3 H2O(g)
We’re given the ΔH˚ and S˚ of each reactant and product:
ΔH° = -726 kJ
S° C2H5OH = 126.8 J/mol K
S° CO2 = 213.7 J/mol K
S° H2O = 188.8 J/mol K
S° O2 = 205.1 J/mol K
We can use the following equation to solve for ΔG˚rxn:
For this problem, we need to do the following steps:
Step 1: Calculate ΔS˚rxn.
Step 2: Use ΔH˚rxn and ΔS˚rxn to calculate for ΔG˚rxn.
For the combustion of one mole of liquid ethanol, ΔH° = -726 kJ. Which answer is closest to ΔG° for this reaction at 2500 °C, given that S° (J/mol K) for C2H5OH is 126.8, for O2 is 205.1, for CO2 is 213.7, and for H2O is 188.8.
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