Activity solubility product

This expression has been written in terms of concentration if activity coefficients sue known or estimated, then a thermodynamically ideal solubility product may be obtained from the Emalogous product of ionic activities. As the concentration of ions in solutions of lanthanide fluorides is low, the concentration and activity solubility products will not differ markedly, although activity coefficients for these salts of 3 + cations are significantly less than unity even in such dilute solutions (4a). 

As indicated previously, AH° can be determined in various ways, and Ss for the solid salt can be obtained from heat capacity measurements, based on the third law of thermodynamics. There remains the evaluation of AF to be considered. If the solubility product K, is known in terms of activities, either by extrapolation of solubility measurements ( 39j) or from electrode potentials ( 45i), AF can be obtained directly, since it is equal to — FT In K as stated above. When the activity solubility product is not available, use may be made of equation (39.70) for the solubility product, i.e.,... 

Molarity, molality, standard state and activity Solubility product constants... 

In this example of the corrosion of zinc in a reducing acid of pH = 4, the corrosion product is Zn (aq.), but at higher pHs the thermodynamically stable phase will be Zn(OH)j and the equilibrium activity of Zn will be governed by the solubility product of Zn(OH)j and the pH of the solution at still higher pHs ZnOj-anions will become the stable phase and both Zn and Zn(OH)2 will become unstable. However, a similar thermodynamic approach may be adopted to that shown in this example. 

Coh ) = concentration (or activity) at the surface which may be obtained from the solubility product of Mg(OH)j, and Aqh- = the mass transport coefficient of hydroxyl ions without chemical reaction and is obtained from ... 

The membrane consists of a binary compound AVaBVb of constant composition. Ion activities in the solid state are 1. At the membrane surface the activities of A and B in the aqueous phase are given by the solubility product ... 

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. 

It must be pointed out that the above calculation is approximate only, and may be regarded merely as an illustration of the principles involved in considering the precipitation of sulphides under various experimental conditions the solubility products of most metallic sulphides are not known with any great accuracy. It is by no means certain that the sulphide ion S 2 is the most important reactant in acidified solutions it may well be that in many cases the active precipitant is the hydrogensulphide ion HS , the concentration of which is considerable, and that intermediate products are formed. Also much co-precipitation and post-precipitation occur in sulphide precipitations unless the experimental conditions are rigorously controlled. 

The silver ions involved are derived from the silver chloride, and by the solubility product principle (Section 2.6), the activity of these ions will be governed by the chloride-ion activity... 

The pressed disc (or pellet) type of crystalline membrane electrode is illustrated by silver sulphide, in which substance silver ions can migrate. The pellet is sealed into the base of a plastic container as in the case of the lanthanum fluoride electrode, and contact is made by means of a silver wire with its lower end embedded in the pellet this wire establishes equilibrium with silver ions in the pellet and thus functions as an internal reference electrode. Placed in a solution containing silver ions the electrode acquires a potential which is dictated by the activity of the silver ions in the test solution. Placed in a solution containing sulphide ions, the electrode acquires a potential which is governed by the silver ion activity in the solution, and this is itself dictated by the activity of the sulphide ions in the test solution and the solubility product of silver sulphide — i.e. it is an electrode of the second kind (Section 15.1). 

Synthesized by soluble guanylyl cyclase and particulate guanylyl cyclase from guanosine triphosphate (GTP). Nitric oxide activates soluble guanylyl cyclase to enhance cyclic GMP production that contributes to various NO actions. Cyclic GMP is hydrolyzed by phosphodiesterases. Cyclic GMP binds to and activates cGMP-dependent protein kinase, phosphodiesterases, and Cyclic Nucleotide-regulated Cation Channels. 

The development of alkylbenzenesulfonates (ABSs) goes back to 1923, when the British chemist Adams discovered that it was possible to obtain water-soluble products by the sulfonation and neutralization of hexadecyl- and octadecyl-benzene. Such products have also soap-like characteristics [1]. In 1926 IG-Farbenindustrie (Hoechst) and Chemische Fabrik Pott, Pirna/Sachsen simultaneously discovered that long-chain ABSs have excellent surface-active properties. 

Solid Bi2S3 does not appear in the expression for K,p, because it is a pure solid and its activity is 1 (Section 9.2). A solubility product is used in the same way as any other equilibrium constant. However, because ion-ion interactions in even dilute electrolyte solutions can complicate its interpretation, a solubility product is generally meaningful only for sparingly soluble salts. Another complication that arises when dealing with nearly insoluble compounds is that dissociation of the ions is rarely complete, and a saturated solution of Pbl2, for instance, contains substantial... 

Solubility equilibria are described quantitatively by the equilibrium constant for solid dissolution, Ksp (the solubility product). Formally, this equilibrium constant should be written as the activity of the products divided by that of the reactants, including the solid. However, since the activity of any pure solid is defined as 1.0, the solid is commonly left out of the equilibrium constant expression. The activity of the solid is important in natural systems where the solids are frequently not pure, but are mixtures. In such a case, the activity of a solid component that forms part of an "ideal" solid solution is defined as its mole fraction in the solid phase. Empirically, it appears that most solid solutions are far from ideal, with the dilute component having an activity considerably greater than its mole fraction. Nevertheless, the point remains that not all solid components found in an aquatic system have unit activity, and thus their solubility will be less than that defined by the solubility constant in its conventional form. 

Assuming that activity of ZnS is unity, solubility product of ZnS ( i-ii) is expressed as,... 

Rard, J.A., "Isopiestic Investigation of Water Activities of Aqueous NiCl2 and CuCl2 Solutions and the Thermodynamic Solubility Product of NiCl2-6H20 at 298.15 K", J. Chem. Eng. Data, 37,433-442 (1992). 

The same expression is obtained if electrodes of the second kind are considered as electrodes of the first kind, where the activity of the metal cations depends on the solubility product of the given insoluble salt (cf. Eq. 3.1.26) ... 

Potentiometry is used in the determination of various physicochemical quantities and for quantitative analysis based on measurements of the EMF of galvanic cells. By means of the potentiometric method it is possible to determine activity coefficients, pH values, dissociation constants and solubility products, the standard affinities of chemical reactions, in simple cases transport numbers, etc. In analytical chemistry, potentiometry is used for titrations or for direct determination of ion activities. 

Sugaya et al. demonstrated the activity of Comamonas sp. TKV3-2-1 for quinoline removal. This aerobic strain utilizes quinoline as carbon and nitrogen source and degrades it to water soluble products [319], No enzymes were identified in this study. 

Electrodes responding to other halides, sulphide, cyanide, silver, lead, copper and cadmium are made using membranes fabricated from pure or doped silver sulphide (Ag2S). The membrane potential is affected by the movement of Ag+ ions between cationic lattice sites which in turn is determined by the activities of the Ag+ ion in the internal and sample solutions. As the activity of the former is fixed, that of the latter alone influences the membrane potential. The electrode will also respond to the presence of S2- ions because of their effect on the Ag+ ion activity via the solubility product expression ... 

An alternative way of expressing the partition constant of a sparingly soluble salt is to define its solubility product Rsp (also called the solubility constant Rs). Ks is defined as the product of the ion activities of an ionic solute in its saturated solution, each raised to its stoichiometric number v . Ks is expressed with due reference to the dissociation equilibria involved and the ions present. 

Changes in solubility product are one means of experimentally determining a value of activity coefficient, because we can independently determine the concentrations (e.g. via a titration) and the values of all y will be one at zero ionic strength. 

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