LearnChemE

Mixing and Solution: Screencast

Illustrates the changes in state variables (V, H, U, S, G) when ideal solutions form. 

We suggest that after watching this screencast, you list the important points as a way to increase retention.

Describes how to use a diagram of enthalpy versus weight percent for a binary mixture to determine the final temperature when mixing is adiabatic. 

We suggest that after watching this screencast, you list the important points as a way to increase retention.

Important Equations:

For an ideal solution

\[H = x_AH_A + x_BH_B\]

where \(H\) = enthalpy (kJ/mol) of the binary solution,

\(x_A\) and \(x_B\)  are mole fractions of the two components,

\(H_A\) and \(H_B\)  are the molar enthalpies (kJ/mol) of the pure components at the same temperature of the solution.

A non-ideal solution can be represented as

\[H = x_AH_A + x_BH_B + \alpha x_Ax_B\]

where \(\alpha\) is a non-ideal parameter.

\[\Delta H_{mix} = H – x_AH_A + x_BH_B\]

where \(\Delta H_{mix}\) = heat of mixing at constant temperature.

For dissolving a solute in a solvent

\[\Delta H_{mix} = H_{solution} – H_{solute} – H_{solvent}\]

\[x_i \gamma _i P_i ^{sat} = y_iP\]

where \(x_i\) = liquid-phase mole fraction of component \(i\)

\(\gamma _i\) = activity coefficient of component \(i\)

\(P_i ^{sat}\) = saturation pressure of component \(i\)

\(y_i\) = vapor-phase mole fraction of component \(i\)

\(P\) = pressure.