Mass-action ratio

The mass-action ratio^[1], often denoted by $\Gamma$ , is the ratio of product concentrations to reactant concentrations.

$\Gamma = \frac{ P_1 P_2 \ldots}{ S_1 S_2 \ldots}$

If the product and reactant concentrations are at equilibrium then the mass-action ratio will equal the equilibrium constant. At equilibrium:

$\Gamma = K_{eq}$

The ratio of the mass-action ratio to the equilibrium constant is often called the disequilibrium ratio, denoted by the symbol $\rho$ .

$\rho = \frac{\Gamma}{K_{eq}}$

At equilibrium $\rho = 1$ . When the reaction is out of equilibrium $\rho < 1$ but always greater than zero.

References

^ B. Hess and K. Brand. (1965). Enzymes and metabolite profiles. In Control of energy metabolism. III. Ed. B. Chance, R. K. Estabrook and J. R. Williamson. New York: Academic Press.

Atkins, P.W. (1978). Physical Chemistry Oxford University Press ISBN 0-7167-3539-X
Trevor Palmer (2001) Enzymes: biochemistry, biotechnology and clinical chemistry Chichester Horwood Publishing ISBN 1-8985-6378-0