What is Chemical equilibrium?
The state a reacting gas reaches when reactions have gone as far as they can and the composition no longer changes.
It tells you how far reactions can go — for example how much \mathrm{CO_2} dissociates into \mathrm{CO} in a hot flame — without needing to know reaction rates.
Leave a gas in a closed container long enough and its composition settles to a fixed state: the equilibrium composition.
Used by the Equilibrium Reactor and the Chemical Equilibrium calculator. Choose what is held fixed: TP (temperature and pressure), HP (adiabatic at constant pressure → adiabatic flame temperature) or SP (entropy and pressure). Solved with Cantera's equilibrium solver.
At fixed temperature and pressure, the equilibrium composition minimizes the Gibbs energy G while conserving each element:
\min_{n_i}\; G = \sum_i n_i \mu_i \quad \text{s.t.} \quad \sum_i a_{ki}\, n_i = b_k
\mu_i is the chemical potential, a_{ki} the number of atoms of element k in species i, and b_k the total amount of element k. For HP and SP, enthalpy or entropy is fixed together with pressure, and temperature is solved for as well.