Acid-dissociation constant water

Acrylic acid is a moderately strong carboxylic acid. Its dissociation constant is 5.5 x 10. Vapor pressure as a function of temperature is given in Table 4 for acrylic acid and four important esters (4,16—18). The lower esters form a2eotropes both with water and with their corresponding alcohols. 

Because of the small size of the fluoride ion, F participates in coordination stmctures of high rank. Tantalum and niobium form stable hexafluorotantalate and hexafluoroniobate ions and hydrogen fluoride attacks these usually acid-resistant metals. Hydrogen fluoride in water is a weak acid. Two dissociation constants are... 

The use of capillary electrophoresis (CE) during the synthetic drug development is described from the preclinical development phase to the final marketed stage. The chapter comprises the determination of physicochemical properties, such as acid—base dissociation constants (pKJ, octanol—water distribution coefficients (logP), and analysis of pharmaceutical counterions and functional excipients. 

Weak acids are not completely ionised in aqueous solution and are in equilibrium with the undissociated acid, as is the case for water, which is a very weak acid. The dissociation constant Ka is given by the expression below ... 

In order to determine to what extent these speculations have validity, it is necessary to be able to evaluate more quantitatively the relative contributions of these interactions to the free energies of protein and nucleic acid molecules in water and nonaqueous solvents. For this purpose, a substantial body of quantitative data is required concerning the properties of suitable model compounds in a variety of solvents, including their solubilities, acid-base dissociation constants, and thermodynamics of hydrogen bond formation. The dearth of pertinent data on hydrogen bonds in solvents of interest is particularly frustrating to even a semiquantitative evaluation of the scheme presented in Fig. 7. 

It is plain from this table that the ratio of the dissociation constants in water and alcohol is not constant. Uncharged acids possess dissociation constants which in alcohol are 10 to 10 times smaller than in water the difference is much less for monovalent cation acids. 

Although hy definition, a pK value is determined in water, analogous "pKa values have been determined in other solvents, too. See for instance K. Izutsu (Ed.), Acid-base dissociation constants in dipolar aprotic solvents. Chemical Data Series No. 35, International Union of Pure and Apphed Chemistry, pubhshed hy BlackweU Scientific Pubhcations, Oxford, London, Edinburgh, Boston, Melbourne, 1990. 

Because it is effective in removing contaminating proteins, the latter method is useful for studying biological interactions with LPS. The phenol-water technique, which was first described by Westphal and Jann (II), takes advantage of the amphopathic nature of the LPS and the solubility of the majority of bacterial proteins in phenol. Polysaccharides, mucopolysaccharides, LPSs with 0-side chains, and nucleic acids are usually soluble in aqueous solutions and insoluble in phenol. Phenol is a weak acid its dissociation constant at 18°C in water is L2 x 10 °. Mixtures of phenol and water have a high dielectric constant. These facts form the basis of a method of partition of proteins and polysaccharides and/or nucleic acids between phenol and water. Minor modifications have been made to the basic protocol described by Westphal et al. (15) and by Johnson and Perry... 

Figure 8.2 Predicted retention of a zwitterion (pK and pK are acid-base dissociation constants in water and micellar solution, respectively, and [S] is surfactant concentration), as a function of pH and micelle concentration with nonionic micelles (top) solute-micelle association constants for cation, zwitterion and anion are 3, 0.1 and 3, respectively, cmc = 2.4x10 M and with anionic micelles (bottom) solute-micelle association constants are 10,000, 10 and 0.1, respectively, cmc = 8.3x10 M. The derivatives of the sigmoidal curves at each micelle concentration are also shown to give the apparent dissociation constants. Reprinted from Ref 6 with permission of the American Chemical Society.

Isotope ratio mass spectrometry International Standards Organization Known or known sample Acid dissociation constant Base disscxdation constant Distribution coefficient Henry s Law constant Solubility product constant Water dissociation constant,... 

It should be noted that the minimum data set, namely molecular mass, Henry coefficient, the octanol/water partitioning ratio and the acid-base dissociation constant, is the same for all environmental fate submodels. 

Knowing the total concentration of a substance, e.g. p-hydroxybenzoic acid, its dissociation constant, the concentration of detergent and Pj, it is a simple procedure to calculate the amount of acid dissolved in the aqueous and micellar phases at different pH values. The results of such a calculation assuming a total concentration of 0.1%w/v p-hydroxybenzoic acid and 5.8 % w/v detergent are given in Table 6.6. If 0.1% w/v is the optimum concentration of acid for a required preservative effect in water at pH 4, the concentration of the unionized acid-the active species-is 5.59 x 10" mol 1" Addition of 5.8% of non-ionic detergent reduces this concentration tol.l4x 10 mol 1" as is seen in column 3 of Table 6.6. 

In pure water, the [H3O ] equals 1.0 x 10 , based on the water dissociation constant, (see Acting as either eui acid or a base Amphoteric water, earlier in this chapter. Using this mathematical relationship, you can calculate the pH ol pure water ... 

This test method covers procedures for the determination of acidic constituents in petroleum products and lubricants soluble or nearly soluble in mixtures of toluene and propan-2-ol (Note I). It is applicable for the determination of acids whose dissociation constants in water are larger than 10 extremely weak adds whose dissociation constants are smaller than I0 do not interfere. Salts react if their hydrolysis constants are larger than 10 . 

Brace [25] detennined dissociation constants of long-chain alkanoic and alkenoic acids featuring a terminal CF3 group in 50% aqueous ethanol, because of limited solubility of the acids in water. Dissociation constants of perfluorooc-tanoic acid and the corresponding unfluorinated alkanoic acids were also measured (Table 3.8). The data revealed that the electron-withdrawing effect of the... 

The dissociation constant of ethanoic (acetic) acid in liquid ammonia is greater than it is in water. Suggest a reason for the difference. 

But a solution of carbon dioxide in water behaves as a very weak acid since the effective dissociation constant K is given by ... 

Acid-base reactions occur when an acid donates a proton to a base. The equilibrium position of an acid-base reaction is described using either the dissociation constant for the acid, fQ, or the dissociation constant for the base, K, . The product of and Kb for an acid and its conjugate base is K (water s dissociation constant). 

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