Calculate Free Energy for Formation

AI Thread Summary
To calculate the standard free energy of formation for phenol (C6H5OH) at 298 K, the standard reaction entropy and reaction enthalpy must first be determined. The equation G = H - TS is used, where G is the free energy, H is the enthalpy, T is the temperature, and S is the entropy. The standard molar enthalpy of combustion for phenol is -3054 kJ/mol, and its standard molar entropy is 144.0 J/(K*mol). By calculating the reaction enthalpy and reaction entropy, the correct value for the standard free energy of formation can be derived. The expected result is -50.42 kJ/mol.
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I realize that this is a chem prob, but I'm stuck with what I thought was a straightforward problem while studying for my physical chemistry exam.

Homework Statement



The standard molar enthalpy of combustion of solid phenol (C6H5OH) is -3054 kJ/mol at 298k and it's standard molar entropy is 144.0 J/(K*mol). Calculate the standard free energy of formation of phentol at 298k.

Homework Equations



G = H - TS

The Attempt at a Solution



G = (-3054.0 * 10^3 J/mol) - (298 K) (144.0 J/k/mol)


From what I know about the determination of G, I simply plugged in those numbers but my solution was way off. The solution should be -50.42 kJ/mol but help with deriving it from first principle is what I'm after.
 
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energy of formation of C6H5OH

you have to calculate the standard reaction entropy first and the reaction enthalpies.

G = rxn enthalpies - (Temp x rxn entropy)

The reaction entropy is: entropy of products - entropy of reactants
the reaction enthalpy is: enthalpy of products - entropy of reactants
 
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