Problem: 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.

FREE Expert Solution

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:


ΔG°rxn=ΔH°rxn-TΔS°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.


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Problem Details

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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