Solubility ionic-strength effect

The basis of these methods is the linear dependence of the absorbance of a solution on the concentration of the various absorbing solutes (Beer s law). Therefore, fundamental requisites are the adherence of the solutes to Beer s law and the constant absorptivity of each one of these species with changing solvent composition. When these requirements are met, the experimentally determined ratio of the concentrations of the ionized to the neutral species (say Q-/Cah) at different pH values leads to thermodynamic pKs (after the appropriate corrections for ionic strength effects). These methods are particularly valuable for the study of sparingly soluble compounds. 

An additional factor was found to influence the rate of reaction in the experiments involving tetrakis ( -mercaptoethylamine) trinickel (II) ion. The addition of nickel chloride retarded the process. Methanol was used as the solvent to demonstrate that the dependence was actually due to the presence of nickel ion and not an ionic strength effect. Magnesium chloride accelerates the rate slightly, while nickel ion greatly retards the rate of reaction. This effect was studied in greater detail, but solubility requirements necessitated the use of a water-methanol mixed solvent. A solution of 5.5M water in methanol was found to be satisfactory to obtain the necessary solubilities of complex and nickel chloride. 

The ionic strength effect is not limited to ksv variation as described by eq. (22). The addition of large amounts of electrolytes may also modify the quencher solubility and thus its efficiency. This effect has been used by some authors, in systems very different from those examined in this work, in order to determine the association constant of the inhibitor salt (Mac, 1997 Mac and Tokarczyk, 1999) as the electrolyte concentration is increased, the quencher ion associates, so that the effective concentration of the inhibitor ion decreases, leading to a downward curvature of the Stern-Volmer plot. Such a curvature can be quantitatively related... 

Figure 2.2. Gypsum (CaS042H20s) solubility data demonstrating the ionic strength effect (salt effect, NaCl) and complexation effect (MgCl2) (from Tanji, 1969b, with permission).

Silver(I) forms a dithiosulfato complex for which /32 = 2 x 10 in dilute aqueous solution at 25 °C. Given that the solubility product of AgBr is 5.3 x 10 (and assuming that ionic strength effects are negligible), show that the minimal total concentration of Na2S203 needed to dissolve 1.00 g silver bromide in 1.00 L of water at 25 °C is 0.0123 mol L . Note that Na+ is introduced simply as the counterion of 8203 and does not enter into the calculations. 

Agl has been extensively studied as a model colloid and historically the studies of surface charging of Agl precede the studies performed with metal oxides. The surface charge and PZC of Agl are defined by the activities of Ag and T ions in the solution [104]. The solubility product of Agl is constant, so only one of these activities can be freely adjusted. The ionic strength effects on the ( potential and of Agl (plotted as a function of pAg) are similar to those shown in Fig. 3.4. 

It follows that as a result of this behavior there are two qualitatively different ionic-strength effects on solubilities, one arising at low / values when the y falls with increasing I, and the other found when y+ increases.with increasing /. Thus, at low ionic strengths the product [Ag" ] [Cl"] will increase with increasing /, because the product [Ag ] [Cl ] y% remains constant and y decreases. Under these conditions added salt increases solubility, and we speak of salting in. 

Calculate the solubility in mg/liter of Cap2 in pure water gt 25°C, neglecting ionic strength effects. 

The solubility of stannous fluoride, SnFe(s), in water at 20 C is 0.012 g/100 ml. What is the solubility of SnFjjs) in a 0.08 M NaF solution neglecting ionic strength effects ... 

What is the solubility of SnF in a 10 mole/liter NaF solution Neglect ionic strength effects. 

Find the solubility of AgCN(s) in distilled water in a closed system volatile HCN can not escape), neglecting ionic strength effects and Ag" " complexes. 

Calculate the conditional solubility product for CaCOsts). Ps CT.caXCr.cOg), where Cy.ca andCr.coj represent the total concentrations of these species in a solution with (a = 10 , pH = 8.7, the temperature = 25 C. Include ionic strength effects. Assume that the only soluble calcium species is Ca +. 

The solubility may differ considerably from the real value when it is calculated as we ve shown through the solubility products. This is the case when supplementary equilibria involving the ionic species figuring in the solubility product are effective. These equilibria may be of several origins. For example, they may be acid-base, redox, or other precipitation equilibria. (In the enumeration of these supplementary equilibria, we have followed the systematic presentation of this book.) Common ion effects may also add themselves to the equilibrium under study. Of course, ionic strength effects may also occur. All these effects are controllable (see the following chapters). 

Soil organics form both soluble and insoluble complexes with metal ions solubility depends on pH, presence of salt or electrolytes (i.e. ionic strength effect), and degree of saturation of organic binding sites (Dempsey et al. 

Stability and solubility constants were largely selected based on their consistency across a number of studies. The consistency may relate to where multiple data are available for a single set of conditions or one or more data are available for multiple conditions (i.e. either temperature or ionic strength). The temperature dependence of stability or solubility constants is based around the relationship of the constants with the inverse of absolute temperature assuming a constant heat capacity (whether zero or non-zero) and that for ionic strength is dependent on the relationship of the constants with respect to the specific ion interaction theory (standard or extended). The consistency is related to the agreement between the measured stability or solubility constants with respect to their uncertainties and the equation used to explain the temperature or ionic strength effects. 

It is important to note that the solubility product relation applies with sufficient accuracy for purposes of quantitative analysis only to saturated solutions of slightly soluble electrolytes and with small additions of other salts. In the presence of moderate concentrations of salts, the ionic concentration, and therefore the ionic strength of the solution, will increase. This will, in general, lower the activity coefficients of both ions, and consequently the ionic concentrations (and therefore the solubility) must increase in order to maintain the solubility product constant. This effect, which is most marked when the added electrolyte does not possess an ion in common with the sparingly soluble salt, is termed the salt effect. 

---