Entropy is a measure of the disorder of a system. Assume the entropy, S, for H₂O is zero at 0 K. The equation for a reaction that produces methanol is shown. CO2(g) + 3H2(g) → CH3OH(g) + H₂O(g) At 298 K, both products of this reaction are liquid. CO2(g) + 3H2(g) → CH3OH(l) + H₂O(l) ΔH° = -131 kJ mol⁻¹ Standard entropies are shown in the table. [Table: substance, S°/JK⁻¹mol⁻¹ for CO2(g), H2(g), CH3OH(l), H2O(l)] In a methanol-oxygen fuel cell, CH3OH(l) and O2(g) are in contact with two inert electrodes immersed in an acidic solution. The half-equation for the reaction at the methanol electrode is shown. CH3OH + H₂O ⇌ CO2 + 6H⁺ + 6e⁻ E° = -0.02 V