#### 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.