Elements of Chemical Reaction Engineering, 6th Edition

C. Thermodynamic Relationships Involving the Equilibrium Constant¹

¹ For the limitations and for further explanation of these relationships, see, for example, K. Denbigh, The Principles of Chemical Equilibrium, 3rd ed. Cambridge: Cambridge University Press, 1971, p. 138.

For the gas-phase reaction

$\begin{matrix} A+ \frac{b}{a} B ⇄ \frac{c}{a} + \frac{d}{a} D & \begin{matrix} (2-2) \end{matrix} \end{matrix}$

The true (dimensionless) equilibrium constant

RTInK = –ΔG

$K = \frac{a_{C}^{c / a} a_{D}^{d / a}}{a_{A} a_{B}^{b / a}}$

where a_i is the activity of species i

$a_{i} = \frac{f_{i}}{f_{i}^{\circ}}$

where

f_i = fugacity of species i

$f_{i}^{\circ}$ = fugacity of species i at the standard state. For gases, the standard state is 1 bar, which is in the noise level of 1 atm, so we will use atm.

$a_{i} = \frac{f_{i}}{f_{i}^{\circ}} = γ_{i} P_{i}$

where γ_i is the activity coefficient

K = True equilibrium constant

K_γ Activity equilibrium constant

K_p

Get Elements of Chemical Reaction Engineering, 6th Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.

Start your free trial

Elements of Chemical Reaction Engineering, 6th Edition by H. Scott Fogler

C. Thermodynamic Relationships Involving the Equilibrium Constant¹

Don’t leave empty-handed

It’s yours, free.

Check it out now on O’Reilly

where	f_i = fugacity of species i
$f_{i}^{\circ}$ = fugacity of species i at the standard state. For gases, the standard state is 1 bar, which is in the noise level of 1 atm, so we will use atm.

C. Thermodynamic Relationships Involving the Equilibrium Constant1

Don’t leave empty-handed

It’s yours, free.

Check it out now on O’Reilly

C. Thermodynamic Relationships Involving the Equilibrium Constant¹