Enthalpy change of mixing

Since the enthalpy change of mixing for ideal gases is zero, the overall enthalpy change for the process is... 

The enthalpy change of mixing can be calculated from Equation (1.74b) ... 

FIGURE 1.8 The enthalpy change of mixing and free energy change as a function of the extent of reaction at 25°C. 

Thus the volume change of mixing A V and the enthalpy change of mixing AH found from the measured quantities AV and Q. Because of its association Q, AH is usually called the heat of mixing. 

For the mixing process at constant pressure, the heat release is equal to the decrease in enthalpy upon mixing according to Example I.E-2. We need to find the enthalpy change of mixing. Eor the addition of dn moles of into the body of mixture containing rip moles of A and ng moles of B, the initial state enthalpy is... 

This is the same as the formula for an ideal gas mixture, Eq. (3.3-20). The enthalpy change of mixing for a solution is given by... 

The enthalpy change of mixing is often expressed in terms of the heat of solution or enthalpy change of solution. For a two-component solution, the molar integral heat of solution of component I in a solution with component 2 is defined by... 

The same enthalpy change of mixing occurs in both equations, but it is divided by the amount of a different substance in each case. 

Similarly, we can understand the enthalpy change of mixing in terms of this hypothetical mixing process at constant T and P. Again, we use the idea that at constant pressure, enthalpy is the appropriate thermodynamic property to characterize energetic... 

For two species, A and B, with a positive enthalpy change of mixing ... 

Volume and enthalpy changes of mixing were discussed in Section 6.3. Can you think of how you might measure the quantities on the right-hand side of Equations (7.74) and (7.75), the volume change of mking and the enthalpy of mixing, respectively, in the laboratory ... 

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