Simulation Details

a) The system of rate equations is integrated by Cash-Karp 5(4) method with a time-step of 0.05 s (using the ODE solver of Ejs).

b) Initial concentrations:

[A]₀ = 0 M; [B]₀ = 1 M; [C]₀ = 0 M

c) Default rate constants:

k_ab = 1s^-1; k_ba =10 s^-1; k_bc = 5 s^-1; k_cb = 0.1 s^-1

For this set of values, the global equilibrium constant is:

K_eq = k_ab* k_bc / k_ba* k_cb = [C]_eq / [A]_eq = 5.00


d) Gibbs energy

For a chemical reaction, at constant temperature T and pressure, the second law of thermodynamics implies that the Gibbs energy change (G_C-G_A) of the reactional system, from non-equibrium to equilibrium states, is:

∆G ⋜ 0, where the = sign means equilibrium.

∆G can be estimated by the well-know equation:

∆G / RT = ∆G^o / RT + ln Q

where R is the ideal gas constant, ∆G^o the standard Gibbs energy (concentrations 1M; p=1 bar)and Q = [C] / [A] the reaction quotient. At equilibrium ∆G = 0 and Q = K_eq, so ∆G^o / RT = - ln K_eq.
Knowing the standard value, the equation gives the Gibbs energy change for concentrations different from the standard ones.

The dimensionless Gibbs energy change is denoted by "G/RT" in the data Table.

Note: The initial values of Q and G/RT (at t=0) were arbitrarily set to 0 in order to avoid numerical indeterminacies or infinities, depending on the chosen set of initial concentrations. They can be "interpreted", however, as indicating that, at instant t=0, the reaction has not yet started.