Ionic strength, calculation

Molar concentrations in millimoles (quantities in parentheses are total ionic strengths calculated from Equation 4), (O) 0.22mM 0.55mM SLS (V) l.OSmM SLS (0 )... 

The same distinction can be made between the actual ionic strength, calculated from the actual concentrations, and the stoichiometric ionic strength. 

Table 4.6 Rate of change of standard transformed entropy of formation in J K moF of inorganic phosphate with pH at three temperatures, five pHs, and three ionic strengths calculated directly...

Fig. 9. Evolution of ionic strength calculated for Bl classic peptisation from measured pH, Al concentration and...

Note that the excess Gibbs energy carries an asterisk to denote that it pertains to the set of components with formally hydrated solutes. Thus, w w is the number of kilograms of "free" water (w w = WwD), and I is the molal ionic strength, calculated in the usual way but with the nominal molalities replaced by molalities corrected for hydration (thus I = I/D). If it were desired to place less reliance on the Debye-Huckel model, other terms could be added to the right hand side in the usual way. We will presently ignore this as we are immediately interested in the hydration correction itself. 

FIGURE 3.2. Ion activity coefficients versus ionic strength /. Calculated from the extended Debye-Hueckel equation. 

Care must be taken in evaluating the ionic strength contribution of weak electrolytes. For example, if any of the solutions above contained phosphoric or acetic acid also, the ionic strength would be essentially the same, because only the dissociated phosphoric or acetic acids contributes, and this is generally very small. If, on the other hand, H3PO4 is the only solute present, then an approximate equilibrium calculation must be carried out (see Example 3.3), an ionic strength calculated, and the process repeated until values of I remain constant. This may take one or two successive approximations. 

Figure 10.17. Variation of the electrostatic interaction energy with separation distance for different ionic strengths, calculated by using the constant-potential assumptions ( s. 30 mV)...

Since it is calculated for the commercial sols that dg averages about 24 A, the mean ionic strength calculated from the equation would be about 0.016 for all the sols. Actually, in a typical 15 nm sol containing about 500 g) of SiOj, the usual stabilizing ratio of SiOsiNajO is about 100 1 and the NajO content is 5 g 1 or about 0.16 N. In such concentrated sols most of the sodium ions must lie very close to the surface (in the Stern layer) leaving a concentration of the order of 0.016 /V in the outer double layer. 

A solution of pure pyruvic acid [CH2=C(OH)COOH] was titrated with pure NaOH solution at the pH meter. Half-way to the equivalence point the meter reading was 2.555. The analytical concentrations calculated from the starting molarities were each 0.0600 M, which i also the ionic strength. Calculate... 

Estimating ionic strength calculating and correcting activity coefficients and dissociation constants for temperature correcting alkalinity for noncarbonate alkalinity. 

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