#### 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.

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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.