# 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:

$\overline{){\mathbf{\Delta G}}{{\mathbf{°}}}_{{\mathbf{rxn}}}{\mathbf{=}}{\mathbf{\Delta H}}{{\mathbf{°}}}_{{\mathbf{rxn}}}{\mathbf{-}}{\mathbf{T\Delta S}}{{\mathbf{°}}}_{{\mathbf{rxn}}}}$

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.

###### 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.