Speed, ionic

Figures 1 through 4 illustrate the effect of Hamaker s constant, disk rotation speed, ionic strength, surface potentials, and particle radius on the rate of deposition of particles onto a rotating disk as computed from Eqs. [lj and [23. For this set of figures, the interaction energy profiles (%) were evaluated from Eqs. 41 5], and 9].

The first term represents the forces due to the electrostatic field, the second describes forces that occur at the boundary between solute and solvent regime due to the change of dielectric constant, and the third term describes ionic forces due to the tendency of the ions in solution to move into regions of lower dielectric. Applications of the so-called PBSD method on small model systems and for the interaction of a stretch of DNA with a protein model have been discussed recently ([Elcock et al. 1997]). This simulation technique guarantees equilibrated solvent at each state of the simulation and may therefore avoid some of the problems mentioned in the previous section. Due to the smaller number of particles, the method may also speed up simulations potentially. Still, to be able to simulate long time scale protein motion, the method might ideally be combined with non-equilibrium techniques to enforce conformational transitions. 

Physical and ionic adsorption may be either monolayer or multilayer (12). Capillary stmctures in which the diameters of the capillaries are small, ie, one to two molecular diameters, exhibit a marked hysteresis effect on desorption. Sorbed surfactant solutes do not necessarily cover ah. of a sohd iaterface and their presence does not preclude adsorption of solvent molecules. The strength of surfactant sorption generally foUows the order cationic > anionic > nonionic. Surfaces to which this rule apphes include metals, glass, plastics, textiles (13), paper, and many minerals. The pH is an important modifying factor in the adsorption of all ionic surfactants but especially for amphoteric surfactants which are least soluble at their isoelectric point. The speed and degree of adsorption are increased by the presence of dissolved inorganic salts in surfactant solutions (14). 

However, it should be mentioned that the dissolution process of a solid, crystalline complex in an (often relatively viscous) ionic liquid can sometimes be slow. This is due to restricted mass transfer and can be speeded up either by increasing the exchange surface (ultrasonic bath) or by reducing the ionic liquid s viscosity. The latter is easily achieved by addition of small amounts of a volatile organic solvent that dissolves both the catalyst complex and the ionic liquid. As soon as the solution is homogeneous, the volatile solvent is then removed in vacuo. 

Obviously, with the development of the first catalytic reactions in ionic liquids, the general research focus turned away from basic studies of metal complexes dissolved in ionic liquids. Today there is a clear lack of fundamental understanding of many catalytic processes in ionic liquids on a molecular level. Much more fundamental work is undoubtedly needed and should be encouraged in order to speed up the future development of transition metal catalysis in ionic liquids. 

The reaction should be relatively fast. (Most ionic reactions satisfy this condition.) In some cases the addition of a catalyst may be necessary to increase the speed of a reaction. 

The uncertainty principle is negligible for macroscopic objects. Electronic devices, however, are being manufactured on a smaller and smaller scale, and the properties of nanoparticles, particles with sizes that range from a few to several hundred nanometers, may be different from those of larger particles as a result of quantum mechanical phenomena, (a) Calculate the minimum uncertainty in the speed of an electron confined in a nanoparticle of diameter 200. nm and compare that uncertainty with the uncertainty in speed of an electron confined to a wire of length 1.00 mm. (b) Calculate the minimum uncertainty in the speed of a I.i+ ion confined in a nanoparticle that has a diameter of 200. nm and is composed of a lithium compound through which the lithium ions can move at elevated temperatures (ionic conductor), (c) Which could be measured more accurately in a nanoparticle, the speed of an electron or the speed of a Li+ ion ... 

The dramatic slowing down of molecular motions is seen explicitly in a vast area of different probes of liquid local structures. Slow motion is evident in viscosity, dielectric relaxation, frequency-dependent ionic conductance, and in the speed of crystallization itself. In all cases, the temperature dependence of the generic relaxation time obeys to a reasonable, but not perfect, approximation the empirical Vogel-Fulcher law ... 

In pseudoplastic substances shear thinning depends mainly on the particle or molecular orientation or alignement in the direction of flow, this orientation is lost or regained at the same speed. Additionally many dispersions show this potential for particle or molecule interactions, this leads to bonds creating a three-dimensional network structure. They are often build-up from relatively weak hydrogen or ionic bonds. When the network is disturbed. 

The speed of agitation governs the rate. The boundary layer thickness decreases at high speeds. A physical process such as the dissolution of an ionic salt in plain water is associated with an activation energy of the order of less than about 5 kcal mol-1. The influence of temperature on physical processes is less pronounced than that from agitation. 

The electrical conduction in a solution, which is expressed in terms of the electric charge passing across a certain section of the solution per second, depends on (i) the number of ions in the solution (ii) the charge on each ion (which is a multiple of the electronic charge) and (iii) the velocity of the ions under the applied field. When equivalent conductances are considered at infinite dilution, the effects of the first and second factors become equal for all solutions. However, the velocities of the ions, which depend on their size and the viscosity of the solution, may be different. For each ion, the ionic conductance has a constant value at a fixed temperature and is the same no matter of which electrolytes it constitutes a part. It is expressed in ohnT1 cm-2 and is directly proportional to the mobilities or speeds of the ions. If for a uni-univalent electrolyte the ionic mobilities of the cations and anions are denoted, respectively, by U+ and U, the following relationships hold ... 

The kaolin was from BDH Ltd. and was dispersed by high-speed stirring at around neutral pH. The resulting suspension was allowed to stand overnight and the sedimented material was rejected. The remaining suspension contained particles up to about 2 ym in size. Final suspensions for the flocculation experiments were made up in 10 3m NaCl, to control the ionic strength. 

The answer to this question depends mainly on the relative speed of the chemical reaction vs. mass transfer of the substrate into the ionic liquid layer. If the chemical reaction is fast vs. the mass transfer rate, a significant part of the reaction will take place at the surface or in the diffusion layer. If the chemical reaction is slow relative to... 

Fig. 17 Plot of the flux, J, of 2-naphthoic acid as a function of the square root of the rotation speed, to, in 0.01 M HC, at an ionic strength p, = 0.5 M (potassium chloride) at 25°C. The error bars represent the standard deviation for each point. (Reproduced with permission of the copyright owner, the American Pharmaceutical Association, from Ref. 114.)...

These uncertainties as to the location of ions such as OH- or F" cast doubt on the validity of the quantitative models which are used to treat micellar rate effects. The problem is less serious for reactions of less hydrophilic ions which bind strongly and specifically to micelles, and it should be relatively unimportant for bimolecular reactions of non-ionic reagents. It is probable also that the volume element of reaction decreases as the concentration of ionic reagent is increased, which would speed reaction. 

In much the same way it should be possible to discriminate between attack by anionic and non-ionic nucleophiles. Micelles, regardless of charge, generally speed attack by non-ionic nucleophiles, but the enhancements are typically small, whereas large inhibition or enhancement is observed for attack of nucleophilic anions, depending upon micellar charge. 

Liquid-liquid biphasic reaction was carried out in a 70-mL autoclave at a stirring speed of 1600 rpm with a catalyst charge of c(Rh) = 0.018x10"5 mol in 4mL ionic liquid. 

The speed of p- and n-type doping and that of p-n junction formation depend on the ionic conductivity of the solid electrolyte. Because of the generally nonpolar characteristics of luminescent polymers like PPV, and the polar characteristics of solid electrolytes, the two components within the electroactive layer will phase separate. Thus, the speed of the electrochemical doping and the local densities of electrochemically generated p- and n-type carriers will depend on the diffusion of the counterions from the electrolyte into the luminescent semiconducting polymer. As a result, the response time and the characteristic performance of the LEC device will highly depend on the ionic conductivity of the solid electrolyte and the morphology and microstructure of the composite. 

Figure 8.6 The effect of stirrer speed on turnover frequency for the hydrogenation of benzene to cyclohexane. (Note that the turnover reaches its maximum at lower stirrer speed for the ionic liquid). , ionic liquid , water...

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