Practice: What are the signs of ∆H, ∆S and ∆G for the spontaneous conversion of a solid into gas?
Gibbs Free Energy represents energy associated with a chemical reaction that can be used to do work.
Gibbs Free Energy
Concept #1: Gibbs Free Energy (∆G)
Example #1: If ∆G is small and positive, which of the following statements is true?
Concept #2: Predicting Spontaneity
Example #2: PCl3 (g) + Cl2 (g) ⇌ PCl5 (g) At 25°C, ΔH° = - 92.50 kJ. Which of the following statements is(are) true?
Practice: Consider the combustion of butane gas and predict the signs of ΔS, ΔH and ∆G.
C4H10(g) + 13/2 O2(g) ⟶ 4 CO2(g) + 5 H2O(g)
Concept #3: Calculations of Gibbs Free Energy
Example #3: For a particular reaction, ΔH = - 111.4 kJ and ΔS = - 25.0 J/K.
Calculate ΔG for this reaction at 298º K. What can be said about the spontaneity of the reaction at 298º K?
Practice: A particular reaction has ΔG = –350 kJ and ΔS = –350 J/K at 24°C. How much heat will be released/absorbed?
Practice: For a reaction in which ΔH = 125 kJ and ΔS = 325 J/K, determine the temperature in Celsius above which the reaction is spontaneous.
