LearnChemE

#### Heterogeneous Chemical Equilibrium: Screencasts

Explains how chemical equilibrium calculations must take material balances into account when have one or more solid phases in equilibrium with one or more gases.

We suggest you list the important points in this screencast as a way to increase retention.

Explains the equilibrium constant for an ideal gas and for a liquid.

We suggest you list the important points in this screencast as a way to increase retention.

# Important Equations

For a liquid mixture, the activity of a component ($$\hat{a}_i$$) is:

$\hat{a}_i \equiv \frac{\hat{f}_i}{f^{\circ}_i} = x_i \gamma _i$

where $$\hat{f}_i$$ = fugacity of component $$i$$ in the mixture,

$$f^{\circ}_i$$ = fugacity of pure component $$i$$ at standard conditions,

$$x_i$$ = mole fraction of component $$i$$

$$\gamma _i$$ = fugacity coefficient of component $$i$$.

The equilibrium constant, $$K_a$$, which is dimensionless, in terms of activities and fugacities:

$K_a = \prod _i \hat{a}_i ^{\nu_i} = \prod _i \left[ \frac{\hat{f}_i}{f^{\circ} _i} \right] ^{\nu _i}$

where $$\prod$$ represents multiplication and $$\nu _i$$ is the stoichiometric coefficient of component $$i$$.

The equilibrium constant depends on temperature:

$exp \left( -\frac{\Delta G^{\circ} _T}{RT} \right) = K_a$

where $$\Delta G^{\circ} _T$$ = change in Gibbs free energy for the reaction at standard conditions and temperature $$T$$, which is an absolute temperature, and $$R$$ = ideal gas constant.