Definition 6.11 University Chemistry — Year 2 · Chapter 6 — Ellingham Diagrams and Metallurgy The Boudouard equilibrium is C(s)+COX2(g)⇌2 CO(g)\ce{C(s) + CO2(g) <=> 2CO(g)}C(s)+COX2(g)2CO(g), endothermic, between carbon and the two oxides of carbon. The Boudouard equilibrium at 1 bar1\,\mathrm{bar}1bar: mole fraction of carbon monoxide in a gas in equilibrium with carbon. Read in context →