Halide ions, hydrated

AS 1 values given in Tables IV and VI. In Fig. 10 the variation of AH with n is shown for the alkali- and halide-ion hydration reactions. It is found for a given alkali ion that the decreases as n increases. Comparing... 

Examining the experimental i, one finds that the entropy change for the alkali- and halide-ion hydration increases with increasing n. It is reasonable to assume that this increase reflects the gradual loss of freedom in the larger clusters due to crowding of the molecules. The entropy changes for the H (H20) ions show the opposite behavior (Table VI), i.e., the... 

Six alkali halide salts KF, RbF, CsF, CsCl, CsBr, and Csl-have an alkali ion radius close to that of the water molecule and a ratio of hydration numbers of alkali ion to halide ion of less than 2. These alkali halides were classified into one group, and calculations based on steric and hydration effects were made to analyze their surface charge. The steric effect, which is related to the size of the alkali ion, halide ion, and water molecule, has Htde influence on the partial hydration of these six alkali halides due to the fact that the radii of alkali ion, halide ion, and water molecule are very close to one another. The other effect, the hydration effect, mainly depends on the ratio of alkali ion hydration number to halide ion hydration number. In this case, since the ratio is less than 2, the influence of hydration is also negligible. The situation for case A is summarized in Table 6. 

AAS detector can also be used with poorer limit of detection. In recent years, inductively coupled plasma-mass spectrometry (ICP-MS) is more and more frequently used as it offers numerous advantages over AAS and AFS detectors. Instead of ethylation, propylation was recently shown to be an even more suitable derivatization method, being free from interferences caused by halide ions. Hydration has also proven to be a useful derivatization method, in particular when coupled with preconcentration by cryotrapping. 

In general, anions are less strongly hydrated than cations, but recent neutron diffraction data have indicated that even around the halide ions there is a well defined primary hydration shell of water molecules, which, in... 

When aluminium is immersed in water, the air-formed oxide film of amorphous 7-alumina initially thickens (at a faster rate than in air) and then an outer layer of crystalline hydrated alumina forms, which eventually tends to stifle the reaction In near-neutral air-saturated solutions, the corrosion of aluminium is generally inhibited by anions which are inhibitive for iron, e.g. chromate, benzoate, phosphate, acetate. Inhibition also occurs in solutions containing sulphate or nitrate ions, which are aggressive towards iron. Aggressive anions for aluminium include the halide ions F ,... 

Persulfate (41) reacts with transition metal ions (e.g. Ag, Fe21, Ti31) according to Scheme 3.42. Various other reduetants have been described. These include halide ions, thiols (e.g. 2-mercaptoethanol, thioglycolic acid, cysteine, thiourea), bisulfite, thiosulfate, amines (triethanolamine, tetramethylethylenediamine, hydrazine hydrate), ascorbic acid, and solvated electrons (e.g. in radiolysis). The mechanisms and the initiating species produced have not been fully elucidated for... 

The solubilities of the ionic halides are determined by a variety of factors, especially the lattice enthalpy and enthalpy of hydration. There is a delicate balance between the two factors, with the lattice enthalpy usually being the determining one. Lattice enthalpies decrease from chloride to iodide, so water molecules can more readily separate the ions in the latter. Less ionic halides, such as the silver halides, generally have a much lower solubility, and the trend in solubility is the reverse of the more ionic halides. For the less ionic halides, the covalent character of the bond allows the ion pairs to persist in water. The ions are not easily hydrated, making them less soluble. The polarizability of the halide ions and the covalency of their bonding increases down the group. 

Lamoureux G, Roux B (2006) Absolute hydration free energy scale for alkali and halide ions established from simulations with a polarizable force field. J Phys Chem B 110(7) 3308-3322... 

The formation of hydrated electrons by the photolysis of halide ions in solution may be envisaged in two steps. The first step is the CTTS absorption leading to (X -). The second step is a slow, thermal process releasing the electron in competition with degradation and recapture. In the presence of acid and alcohol, photolysis of halide solutions generates H2 with a yield that increases both with acid and alcohol concentrations (seejortner et al., 1962, 1963, 1964). At 25°, the limiting quantum yields are 0.98 for Cl- at 185 nm, 0.6 and 0.5 for Brat 185 and 229 nm, respectively, and 0.3 and 0.25 for I- at 254 and 229 nm, respectively. Since most of these yields are less than 1, the direct reaction of HsO and (Xaq-) is ruled out. Instead, it is proposed that eh is produced from the... 

We shall now turn our attention to the results obtained for the hydration of alkali- 128,130,isi, 158) and halide ions 135,131,133,139 which have been the focus of all kinds of theoretical calculations. Some features are clearly evident from the gas-phase solvation data (Table 8). 

The strong hydration of halide ions in water is partly due to outer-sphere effects. Oxo anions in aqueous solution may complex with outer-sphere water molecules as in the hydrated chromate and permanganate ions ... 

Cd2+, though the stabihty differences between the various halides are very much smaller than for Hg2+ (Table 2). On the other baud, for Zn2+ the impact of the AHn terms has become so small that an (a) or hard sequence results on account of the increase of JSb occurring as the halide ion becomes smaller and consequently more strongly hydrated. 

Conditions existing at the triple interface, Ag/AgX/Solution, will influence the rate at which the catalyzed reaction occurs. These conditions will determine the activity of the silver ions, the concentration of adsorbed developer, and the state of the catalyst. The halide ion will be an important factor in determining the activity of the silver ions, and Sheppard has suggested that the hydration and diffusion away of the halide ion is the dominant factor in determining the specific rate of reaction at the interface (Sheppard, 15). The known order of reactivity of the halides, AgCl > AgBr > Agl, follows as a natural consequence from this point of view, whereas it would not be predicted on the basis of the electrode mechanisms. 

Nucleophilic addition to C=0 (contd.) ammonia derivs., 219 base catalysis, 204, 207, 212, 216, 226 benzoin condensation, 231 bisulphite anion, 207, 213 Cannizzaro reaction, 216 carbanions, 221-234 Claisen ester condensation, 229 Claisen-Schmidt reaction, 226 conjugate, 200, 213 cyanide ion, 212 Dieckmann reaction, 230 electronic effects in, 205, 208, 226 electrons, 217 Grignard reagents, 221, 235 halide ion, 214 hydration, 207 hydride ion, 214 hydrogen bonding in, 204, 209 in carboxylic derivs., 236-244 intermediates in, 50, 219 intramolecular, 217, 232 irreversible, 215, 222 Knoevenagel reaction, 228 Lewis acids in, 204, 222 Meerwein-Ponndorf reaction, 215 MejSiCN, 213 nitroalkanes, 226 Perkin reaction, 227 pH and, 204, 208, 219 protection, 211... 

The hydration of anions is regarded as being electrostatic with additional hydrogen bonding. The number of water molecules in the primary hydration sphere of an anion depends upon the size, charge and nature of the species. Monatomic anions such as the halide ions are expected to have primary hydration spheres similar to those of monatomic cations. Many aqueous anions consist of a central ion in a... 

The conventional enthalpies of hydration of the uni-negatively charged halide ions may be estimated using the thermodynamic cycle shown in Figure 2.8. 

The reactions considered here are the formations of the hydrated halide ions when the halogen molecules react with dihydrogen to give the hydrated proton and the hydrated halide ions. 

Since the second term on the left-hand side of equation (2.20) is conventionally set to zero, the equation may be used to estimate conventional values of enthalpies of hydration for a series of halide ions. The left-hand side of the equation (2.20) represents the conventional value of the enthalpy of hydration of the X- ion ... 

When an absolute value for the enthalpy of hydration of the proton is used in equation (2.22) it would have the effect of making the absolute enthalpies of hydration of the halide ions considerably less negative than the conventional values. 

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