Question

Given the values of So given below in J/mol K and of ΔHfo given in kJ/mol, calculate the value of ΔGo in kJ for the combustion of 1 mole of methane to form carbon dioxide and gaseous water at 298 K. S (CH4(g)) = 189 S (O2(g)) = 200 S (CO2(g)) = 210 S (H2O(g)) = 186 ΔHfo (CH4(g)) = -75 ΔHfo (CO2(g)) = -396 ΔHfo (H2O(g)) = -220

Answer 1

-759 kJ

Step-by-step explanation:

The reaction is

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g)

And, ΔG° = ΔH° - TΔS°

Where T is the temperature in K.

ΔH° = ∑n*H°f, reactants - ∑n*H°f, products

Where n is the number of moles in the stoichiometry reaction. H°f,O₂(g) = 0 because it's a substance formed by only one element.

ΔH° = [2*(-220) +(-396)] - [-75] = -761 kJ

ΔS° = ∑n*S°, reactants - ∑n*S°, products

ΔS° = [2*(186) + 210] - [2*200 + 189] = -7 J/K = -0.007 kJ/K

So

ΔG° = -761 - 298*(-0.007)

ΔG° = -759 kJ