Ionic yield, definition

Since the fraction of electrons and holes, although very small, depends on the (local) oxygen potential and since the mobility of the electronic defects is far larger than that of the ionic defects, the electronic conductivity may, by continuously changing the oxygen potential, eventually exceed the ionic conductivity. By definition, the transference number is t-loa = erion/(crion + crei)> which explicitly yields... 

The first clear definition of acidity can be attributed to Arrhenius, who between 1880 and 1890 elaborated the theory of ionic dissociation in water to explain the variation in strength of different acids.3 Based on electrolytic experiments such as conductance measurements, he defined acids as substances that dissociate in water and yield the hydrogen ion whereas bases dissociate to yield hydroxide ions. In 1923, J. N. Brpnsted generalized this concept to other solvents.4 He defined an acid as a species that can donate a proton and defined a base as a species that can accept it. This... 

This important equation expresses the fact that the conductance A of a solution is an additive property and that it equals the sum of the cation conductance X+ and of the anion conductance X. When applying the equation (111-21) we must, however, bear in mind that the ionic conductances Af and A (as well as the velocities y+ and v ) are dependent on concentrations, so that in every particular case their respective values have to agree with the composition of the solution in question. Apart from this it must be remembered that the mutual electrostatic attractions of ions vary at definite concentrations according to the nature of the electrolyte so that the equation (III-21) does not. always yield quite accurate results for arbitrary combinations of cations and anions. 

Sensitivity the sensitivity of an instrument is the ratio of the ionic current change to the sample flux change in the source (in Cqg-1). The analytical sensitivity is the smallest quantity of compound yielding a definite signal-to-noise ratio, often 10 1. 

Inst as compounds have definite ratios of elements, chemical reactions have definite ratios of reactants and products. Those ratios are used in Section 10.1 to calcnlate the number of moles of other substances in a reaction from the nnm-ber of moles of any one of the snbstances. Section 10.2 combines information from Section 10.1, Chapter 7, and elsewhere to explain how to calcnlate the mass of any substance involved in a reaction from the mass of another. Section 10.3 demonstrates how to work with qnantities in nnits other than moles or masses when finding quantities of reactants or prodncts. Section 10.4 shows how to calcnlate the quantities of snbstances involved in a reaction even if the quantities of reactants present are not in the mole ratio of the balanced equation. Section 10.5 covers the calculation of the percentage yield of a product from the actual yield and the theoretical yield, based on the amonnt(s) of reactant(s). Section 10.6 explains which of these types of calcnlations can and cannot be done with net ionic equations. 

Unfortunately, the calculated values of yt cannot be confirmed by direct experiment, because in principle all experimental methods yield the mean activity coefficient y rather than the individual ionic values. By use of the definition given in (2-16), the experimentally determined value can be apportioned to give nd y. This procedure is theoretically justified only at high dilution, where the DHLL is valid because the limiting slope of log y plotted against /n is found experimentally to be O.SZ Zb, as required by (2-17). At higher values of n the ion-size parameter a must be introduced. 

For the specific case of a standard for fluoride ion activity KF rather than NaF has been suggested. KF is a better choice because ion pairing is much less. Further, the average hydration number of the fluoride ion is almost the same as that for potassium ion, so that activity coefficients of the two ions are similar. Suggested reference activity values (pM or pAJ for use in the operational definitions for ion-activity measurements [Equations (13-26) or (13-27)] are shown in Table 13-2. For the case of fluoride ion, measurements of its activity in NaF-NaCl mixtures up to 1 m and KF-KX mixtures up to 4 m yielded the same values as pure NaF or KF at the same ionic strength. 

Let us consider first a surface-inactive solution, whose properties have already been outlined in Sects. 2.1.3 to 2.1.6. By definition, this term means that the compact layer is solely composed of solvent molecules. The distribution of components within the diffuse layer is determined mostly by the electrostatic forces. If the image forces (see Sect. 2.1.11.3) can be disregarded the concentrations of solute species, ionic or neutral, at the p.z.c. are identical to their bulk values, and the integral (66) over the diffuse layer vanishes. Inside the compact layer the concentration, Ci(z), is zero, and the integration in (66) yields Eq. (12) for the Gibbs adsorption of surface-inactive components, F = —zhc, which allows one to measure the thickness of the ion-free layer of the solvent, zh-... 

An unparalleled variety of reactant species may be prepared in the flowing afterglow technique, the range being illustrated by H", Fe, AlO", and NO (H20)3 for ionic reactants and by O, 02( A), and O3 for neutral reactants. Yet the unique and outstanding contribution of the technique has been its ability to yield rate constants which are truly thermal, i.e., which relate to a Maxwell-Boltzmann distribution for a definite temperature, which distribution is always maintained by the buffer gas, irrespective of the rate of the reaction studied. (Spectroscopic measurements have established in several cases that the reactant ions have been relaxed to this characteristic Maxwell-Boltzmann distribution before they enter the reaction region.) A wealth of data are now available for such thermal... 

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