Stoichiometric mean ionic activity coefficients

This has always been an important, though very indirect, source of hydration numbers. Colligative properties and emfs give high precision experimental data from which the activity of the solute can be calculated and stoichiometric mean ionic activity coefficients found. If it is assumed that solvent molecules are bound to the ions, a relation between... 

Fig. 17.4. Stoichiometric mean ionic activity of HCl (a ,Hci) versus molality of HCl. Crosses are data points from Table 17.2 dotted line is Henry s Law, having an activity of 1.0 at 1.0 molal HCl. The stoichiometric mean ionic activity coefficient at muci =0J sxy/xz = 0.772.

J. C. Poirier, Thermodynamic functions from Mayer s theory of ionic solutions. II. The stoichiometric mean ionic molar activity coefficient, /. Chem. Phys. 21,972 (1953). 

The Debye-Hiickel equation in terms of stoichiometric mean ionic activity coefficients is (where yn indicates it is a Henryan activity coefficient)... 

Figure 15.4 Curves labeled k= , etc., are calculated from Equation (15.22). Diamond symbols are stoichiometric mean ionic activity coefficients for NaCl at 25°C from the EoS of Archer (1992) as a function of (stoichiometric) ionic strength. The curve through the diamond symbols is calculated using Equation (15.28)...

The activity of each ionic species may be represented as the product of its molality and its (stoichiometric) activity coefficient hence is equal to my. and oci to 2my, where m is the molality of the zinc chloride solution in the cell. By equation (39.9), 7+7I is equal to y , where y is the mean ionic activity coefficient hence equation (45.16) becomes... 

Therefore other classes of activities and activity coefficients are defined ( mean ionic activities and mean ionic activity coefficients, without the stoichiometric ), which are related to the stoichiometric quantities by the degree of dissociation, a, where... 

Recall that y is the mean ionic activity coefficient of a strong electrolyte, or the stoichiometric activity coefficient of an electrolyte that does not dissociate completely. 

---