Self-ionization degree

The molecules of amphiprotic solvents which are the most important will be designated as SH. Self-ionization occurs to a small degree in these solvents according to the equation... 

The activity of the solvent molecule HS in a single-component solvent is constant and is included in Kus. The concentration of ions is mostly quite low. For example, self-ionization occurs in water according to the equation 2H20— H30+ + OH". The conductivity of pure water at 18°C is only 3.8 X 10"8 Q"1 cm-1, yielding a degree of self-ionization of 1.4xl0"19. Thus, one H30+ or OH" ion is present for every 7.2 x 108 molecules of water. Some values of Kus are listed in Table 1.5 and the temperature dependence of the ion product of water Kw is given in Table 1.6. 

If the solvent is not protogenic but protophilic (acetone, dioxan, tetrahydrofuran, dimethylformamide, etc.), self-ionization obviously does not occur. Consequently, the dissolved acids are dissociated to a greater or lesser degree but dissolved bases do not undergo protolysis. Thus, there can exist only strong acids but no strong bases in these solvents. The pH is not defined for a solution that does not contain a dissolved acid (i.e. in the pure solvent or in the solution of a base). The pKA value can be defined but not... 

Pure water spontaneously self-ionizes to a small degree, leading to equal concentrations of hydrogen and hydroxide ions (1 x 10 mol/L, or 1 x 10 M) ... 

Organic donor molecules appear to facilitate reactions with metals by increasing the degree of self-ionization of the solvent as a result of adduct formation with the [NO] cation e.g. Cu dissolves in liquid N204/MeCN... 

These facts suggest the association of acidity with the aqueous ion and basicity with the aqueous OH ion. An acidic solution is then one that contains more ions than pure water does and a basic solution one that contains more OH ions. Pure water has a very slight conductivity, attributed to low concentrations of H and OH ions ( 10 M at 25 °C), arising from a small degree of self-ionization ... 

The characteristics of the self-assemblies based on F(nBA2o%-stat-AAso%)ioo-b- M5 dispersed in aqueous solution were then measured by means of static and dynamic light scattering (SLS and DLS) and small angle neutron scattering (SANS) as a function of the ionization degree a of the AA units in the polymer. The value of a was adjusted by adding the proper amount of NaOH (see Material and Methods ). For a > 20% and in the presence of O.IM NaCl, DLS indicates the presence of two populations of scatterers... 

The degree of self-ionization depends on both the acid strength and the basic strength of the molecule. For example, for water (assuming molar concentrations approximate to activities H+ is in some standard state, perhaps in the gas phase),... 

Some polar fluids exhibit a small degree of ion formation even in the liquid state at room temperature and at ordinary pressure. This self ionization can be of considerable influence on the dissociation equilibria of dissolved electrolytes. The phenomena of solvolysis or hydrolysis in aqueous systems depend on the... 

Experimental determinations of the conducting properties of electrolyte solutions are important essentially in two respects. Firstly, it is possible to study quantitatively the effects of interionic forces, degrees of dissociation and the extent of ion-pairing. Secondly, conductance values may be used to determine quantities such as solubilities of sparingly soluble salts, ionic products of self-ionizing solvents, dissociation constants of weak acids and to form the basis for conductimetric titration methods. 

The majority of widely used room-temperature solvents possess negligible degree of the self-ionization, therefore, the initial and the equihbrium concentrations of solvent molecules are constant and they are practically the same. The term in the denominator can be entered as the constant, which gives the following final form ... 

From Eq. [9.2.12], it follows, that the solvosystem concept is appropriate for the description of acid-base interaction in any molecular solvent with relatively small ionic product and, consequently, low degree of self-ionization. In particular, it may be used for description of interactions in covalent halide melts and aluminum, zinc and cadmium halides should be mentioned among such solvents. In relation to aeid and base terms... 

There are at least two ways by which lipids can affect protein structure and function and thereby cell function. Protein function is influenced by specific protein-lipid interactions that depend on the chemical and structural anatomy of lipids (head group, backbone, alkyl chain length, degree of unsaturation, chirality, ionization, and chelating properties). However, protein function is also influenced by the unique self-association properties of lipids that result from the collective properties (fluidity, bilayer thickness, shape, and packing properties) of the lipids organized into membrane structures. 

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