11of hydration,kcal/molPredictedExperim.TableCationAnion1.2+LiF112.0109.6-Sign of+NaF88.4+109.6theKF71.1++109.6surfaceRbF65.9109.6++chargeCsF58.2109.6++forselecteLiCI82.5112.0--d alkaliNaCl88.482.5+-halidesKCI+71.182.5-(MillerKCI*+71.182.5+&RbCl65.982.5++YalamCsCI58.282.5++anchili,1994).LiBr112.075.7--*Laser88.475.7NaBr--qualityKBr71.175.7+-KCLRbBr65.975.7+1+58.275.7+CsBr1.4.ElectricaldoublelayerDue to the reasons discussed in the preceding section, solid particles in water are almostalways electrically charged. Some ions will be adsorbed on such surfaces, some will bedistributed according to the influence of electrical forces and thermal motion. The formerform an inner region of the electrical double layer (adsorbed layer), the latter a diffusedregion,This situation is shown below
11 Table 1.2 Sign of the surface charge for selecte d alkali halides (Miller & Yalam anchili, 1994). *Laser quality KCl. 1.4. Electrical Electrical Electrical Electrical double layer Due to the reasons discussed in the preceding section, solid particles in water are almost always electrically charged. Some ions will be adsorbed on such surfaces, some will be distributed according to the influence of electrical forces and thermal motion. The former form an inner region of the electrical double layer (adsorbed layer), the latter a diffused region. This situation is shown below. of hydration, kcal/mol Predicted Experim. Cation Anion LiF NaF KF RbF CsF LiCl NaCl KCl KCl* RbCl CsCl LiBr NaBr KBr RbBr CsBr 112.0 88.4 71.1 65.9 58.2 112.0 88.4 71.1 71.1 65.9 58.2 112.0 88.4 71.1 65.9 58.2 109.6 109.6 109.6 109.6 109.6 82.5 82.5 82.5 82.5 82.5 82.5 75.7 75.7 75.7 75.7 75.7 - + + + + - - + + + + - - + + + + + + + + - + - + + + - - - - +
12SHRACECOUNTERIONSA-ODISTANCE(1.22)2+22YBrHP-InnerHelmholtzPlaneOHP-OuterHelnhoitzPlane(Stern plane)Grahamemodeloftheelectricaldoublelayer(inthepresenceofspecificallyadsorbingions)OHPTHPFig.1.13.Electrical doublelaverwithoutspecificadsorptionofions(A).Graememodeoftheelectrical doublelayer(inthepresenceof specificallyadsorbing ions)(B)
12 Fig. 1.13. Electrical double layer without specific adsorption of ions (A). Graeme model of the electrical double layer (in the presence of specifically adsorbing ions) (B). (1.22) A B