Chemical reaction equilibrium involving ions

Electrode processes are a class of heterogeneous chemical reaction that involves the transfer of charge across the interface between a solid and an adjacent solution phase, either in equilibrium or under partial or total kinetic control. A simple type of electrode reaction involves electron transfer between an inert metal electrode and an ion or molecule in solution. Oxidation of an electroactive species corresponds to the transfer of electrons from the solution phase to the electrode (anodic), whereas electron transfer in the opposite direction results in the reduction of the species (cathodic). Electron transfer is only possible when the electroactive material is within molecular distances of the electrode surface thus for a simple electrode reaction involving solution species of the fonn... 

If auxiliary chemical reactions are involved in concentration determinations using ion-selective electrodes (end point titration, standard addition or subtraction, indirect procedures), extreme caution is required with variable sample temperatures. This is because in addition to the electrochemical effects discussed, purely chemical phenomena may become problematic (temperature dependence of equilibrium constants, solubility products, complex formation constants and activity coefficients). With the low sample flow rates commonly encountered (a few ml/minute), thermostating the solution and sample cell with the help of a quickly responding proportional controller (Orion, Series 1,000) presents no problem. 

The Gibbs phase rule is the basis for organizing the models. In general, the number of independent variables (degrees of freedom) is equal to the number of variables minus the number of independent relationships. For each unique phase equilibria, we may write one independent relationship. In addition to this (with no other special stipulations), we may write one additional independent relationship to maintain electroneutrality. Table I summarizes the chemical constituents considered as variables in this study and by means of chemical reactions depicts independent relationships. (Throughout the paper, activity coefficients are calculated by the Debye-Hiickel relationship). Since there are no data available on pressure dependence, pressure is considered a constant at 1 atm. Sulfate and chloride are not considered variables because little specific data concerning their equilibria are available. Sulfate may be involved in a redox reaction with iron sulfides (e.g., hydrotroilite), and/or it may be in equilibrium with barite (BaS04) or some solid solution combinations. Chloride may reach no simple chemical equilibrium with respect to a phase. Therefore, these two ions are considered only to the... 

From Eqn. (14) it follows that with an exothermic reaction - and this is the case for most reactions in reactive absorption processes - decreases with increasing temperature. The electrolyte solution chemistry involves a variety of chemical reactions in the liquid phase, for example, complete dissociation of strong electrolytes, partial dissociation of weak electrolytes, reactions among ionic species, and complex ion formation. These reactions occur very rapidly, and hence, chemical equilibrium conditions are often assumed. Therefore, for electrolyte systems, chemical equilibrium calculations are of special importance. Concentration or activity-based reaction equilibrium constants as functions of temperature can be found in the literature [50]. 

We have mentioned salts in solution (i.e., dissolved in water), reversible reactions and equilibrium in solution, and ions in solution. Most chemical reactions occur in solution. It was apparent to Van t Hoff at an early stage that to understand the dynamics and thermodynamics of chemical reactions, he needed to understand the nature of solutions in general. And it was equally clear when he began his work that very little was known about the nature of solutions. Solutions always involve specific chemicals, the solvent (often water) and the dissolved substance or solute (often a salt, e.g., sodium chloride). But although they are always chemical systems, they can also be considered as physical systems, to which the principles of thermodynamics can be applied. 

IR-spectra of pseudostrychnine in the solid phase and in solution indicate that it exists almost entirely in the carbinolamine form CXCVI. Two other forms might be expected to exist in equilibrium with CXCVI in solution the immonium form CXCVII, produced by proton-catalyzed loss of the hydroxyl group, is totally excluded on steric grounds the keto-amine form CXVIII, on the other hand, almost certainly exists in equilibrium with CXCVI in solution, but in concentrations which escape detection by physical methods. Its presence is deduced from some of the chemical reactions of pseudostrychnine. The easy formation of O-alkyl ethers (125) by interaction with methanol or ethanol even at room temperature almost certainly involves nucleophilic attack of the alcohol molecule on the carbonyl carbon in CXCVIII or in the O-protonated form CXCIX (R = H) to yield a hemiacetal as a first step likewise, the formation of 16-cyanostrychnine (XXV CN instead of OH) must involve addition of cyanide ion to CXCVIII, and the reaction with... 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

In the model it is proposed that during the exchange RA + B O RB + A involving a chemical reaction of the counterions, B and A, with the resin site, R, they exist in the exchanger in two states, namely free and as the species formed by their combination with R. Counterions B and A are considered to be immobile vdiile bound and to move unimpeded while free. Ideally, ion concentrations in the free and bound states (c, and a respectively) are related to the dissociation constants, K, of the complexes Ri by the equilibrium relations for the complexation reactions. These dissociation-association equilibria have the form... 

As with any other chemical reaction, the formation of a metal complex from a metal ion and a set of proligands can be described by an equilibrium constant. In its simplest form, a complexation reaction might involve the reaction of unsolvated metal ions in the gas phase with gas phase proligands to form a complex. In practice it is difficult to study such reactions in the gas phase and complex formation is normally studied in solution, often in water. This introduces the complication that the solvent can also function as a ligand, so that complex formation will involve the displacement of solvent from the metal coordination sphere by the proligand. 

The effect of transfer, from dimethylacetamide or dimethylformamide to 88 % MeOH-HgO or methanol, on a number of chemical processes involving bromide ion, such as the equilibrium constant for (31), the forward rate constant for (31) (Mac et al., 1967), the rate constant for reaction of bromide ion with methyl iodide (Parker, 1966), or with 2,4-dinitroiodobenzene (Parker, 1966), the redox potential of the Br /Brj couple (Parker, 1966), and the association constant for Br formation (Parker, 1966), can all be accounted for on the assumption that o/Br- is ca. 10 and that solvent activity coefficients of other species which are involved in the processes are unity or cancel each other. 

As you know, oxidation-reduction reactions can involve molecules, ions, free atoms, or combinations of all three. To make it easier to discuss redox reactions without constantly specilying the kind of particle involved, chemists use the term species. In chemistry, a species is any kind of chemical unit involved in a process. For example, a solution of sugar in water contains two major species. In the equilibrium equation NH3 + H2O NH/ + OH , there are four species the two molecules NH3 and H2O and the two ions NH/ and OH. ... 

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