a. i. Define standard free energy change of formation.

ii. Write a balanced equation to represent the standard free energy change of formation of ethane. Include state symbols in your answer.

b. The standard free energy change of formation of ethane is –32.9 kJ mol^–1. The standard entropy change of the system for this reaction is –173.7 J K^–1 mol^–1.

i. State the relationship between standard free energy change of formation, standard entropy change of the system and the enthalpy change.

ii. Explain why the reaction can be regarded as spontaneous, even though the value of the standard entropy change of the system is negative.

c. Ethane undergoes combustion to form carbon dioxide and water.

C₂H₆(g) + 3 1/2 O₂(g) → 2CO₂(g) + 3H₂O(l)

Calculate the free energy change of combustion for this reaction.

(Values for ΔG^θ in kJ mo^l–1: C₂H₆(g) = –32.9, CO₂(g) = –394.4, H₂O(l) = –237.2)