Exemplar Problems

Problem 17 :For a chemical reaction, the standard enthalpy change (∆H°) is -50 kJ/mol, and the standard entropy change (∆S°) is 100 J/(mol•K). Calculate the standard Gibbs free energy change (∆G°) at 25°C (298 K).

Solution :

The relationship between ∆G°, ∆H°, ∆S°, and temperature (T) is given by the equation: ∆G° = ∆H° - T∆S°

∆G° = (-50,000 J/mol) - (298 K * 100 J/(mol•K)) ∆G° = -50,000 J/mol - 29,800 J/mol ∆G° = -79,800 J/mol ≈ -79.8 kJ/mol

So, the standard Gibbs free energy change (∆G°) at 25°C is approximately -79.8 kJ/mol.