Sulfur trioxide is produced industrially by the gas-phase reaction
2 SO₂(g) + O₂(g) ⇌ 2 SO₃(g).
At 600 K, tabulated thermodynamic data give ΔH° = –198 kJ mol⁻¹ and ΔS° = –187 J mol⁻¹ K⁻¹ (assumed constant with temperature). The gas constant is R = 8.314 J mol⁻¹ K⁻¹.
An experimental study measures the equilibrium constant at 600 K to be K_exp = 4.2 × 10⁶.
(a) Calculate the standard Gibbs free-energy change ΔG° for the reaction at 600 K.
(b) Determine the theoretical equilibrium constant K_pred at 600 K based on the thermodynamic data provided.
(c) Calculate the percent difference between K_pred and the experimental value K_exp.
(d) Propose two plausible factors that could account for the discrepancy between K_pred and K_exp. Justify each factor in the context of the experimental system.