Question

# Estimate the free energy change (?Grxn) for the following reaction at 298 K, if each gaseous...

Estimate the free energy change (?Grxn) for the following reaction at 298 K, if each gaseous substance is present at p = 0.25 atm.

C2H5OH(l) + 3O2(g) ? 2CO2(g) + 3H2O(l)

ENTHALPY OF REACTION

[2ΔHf(CO2 (g)) + 3ΔHf(H2O (g))] - [1ΔHf(C2H5OH (ℓ ethanol)) + 3ΔHf(O2 (g))]

[2(-393.51) + 3(-241.82)] - [1(-276.98) + 3(0)] = -1235.5 kJ

-1,235.50 kJ (exothermic)

ENTROPY CHANGE

[2ΔSf(CO2 (g)) + 3ΔSf(H2O (g))] - [1ΔSf(C2H5OH (ℓ ethanol)) + 3ΔSf(O2 (g))]

[2(213.68) + 3(188.72)] - [1(161.04) + 3(205.03)] = 217.39 J/K

217.39 J/K (increase in entropy)

FREE ENERGY OF REACTION (AT 298.15 K)

From ΔGf° values:

[2ΔGf(CO2 (g)) + 3ΔGf(H2O (g))] - [1ΔGf(C2H5OH (ℓ ethanol)) + 3ΔGf(O2 (g))]

[2(-394.38) + 3(-228.59)] - [1(-174.18) + 3(0)] = -1300.35 kJ

-1,300.35 kJ (spontaneous)

From ΔG = ΔH - TΔS:

-1300.31 kJ (spontaneous)

EQUILIBRIUM CONSTANT, K (AT 298.15 K)

6.6702167631e+227

This process is favorable at 25°C.