The ionization constant K

The answer is in the expression for the ionization constant, K l or Kb, where the ratio of the conjugate acid and base concentrations is found. In the case of a weak monoprotic acid, HA, we have the following ... 

The molecular conductivity of periodic acid in soln. containing one mol. in v litres of water has been determined by W. Ostwald,14 A. Rosenheim, and E. Lowenthal. The two sets of determinations are concordant. F. Kohlrausch gives 48 and 64 for the mobilities of the 10/ and C10/-ions respectively on the assumption that this ionization is HI04=H-+I0/, the calculated ionization constant K does not change much with. .dilution. Assuming the mobility of the hydrogen is 338 at 25°, V. Rothmund and K. Drucker have calculated the degrees of ionization, a, and the ionization constants K, from W. Ostwald s eq. conductivities A ... 

The percentage degree of ionization, a and the ionization constant K% are also indicated. Hence, the first ionization constant is rather weaker than that of ammonium hydroxide, being somewhere near A1=3xl0-8. I. M. Kolthoff calculated for the second ionization constant of hydrazine, i 2—2-8 X10 3 and E. C. Gilbert said that it should be less than 10 12. P. Drude gave 53 for the dielectric constant at 22°. 

Acetic acid in 0.1 molal solution is 1.4 per cent ionized. Find the value of the ionization constant K. 

Consider the dissolution of a metal M as given by reaction 5.3. The ionization constant K for this reaction is defined as... 

When experimental data are available for k as a function of [H+], three unknown coefficients have to be evaluated for a process for which k is given by eqn. (5) and five unknown coefficients for one when k is given by eqn. (6). It is advisable to carry out separate determinations of the ionization constants K, or K, and K2, respectively, (concentration constants valid for the ionic strength of the kinetic experiments) whenever possible with a reasonable precision. These determinations should be done with the aid of appropriate potentiometric or photometric methods [8,9] independent of the kinetic measurements. As soon as the ionization... 

Exact calcnlations of simnltaneons eqnilibria can be complicated. They simplify considerably when the original acid concentration is not too small and the ionization constants K i and K 2 differ snbstantially in magnitnde (by a factor of 100 or more). The latter condition is almost always satisfied. Under such conditions, the two equilibria can be treated sequentially, as in the following example. 

Calculate the hydrogen ion (H+) concentration in a 0.1-M HCNO solution. What is the degree of ionization of cyanic acid in this same solution The ionization constant, K, for the acid is 2 x lO. ... 

A 0.055 M aqueous solution of a weak, monoprotic acid is 0.85% ionized. Calculate the value of the ionization constant, K, for this acid. 

The ionization constant, K, for propanoic acid, CyHjCOOH, is 1.3 X 10 . What is the percent ionization in a 0.65 M solution of propanoic acid Propanoic acid is a monoprotic acid. 

From this development it can be seen that the pH produced by a mixture of a weak acid and its salt will depend primarily upon the ionization constant, K, of the weak acid. In addition, since K differs from K by the activity coefficient f (f can be assumed to be nearly unity) the pH values will depend upon the ionic strength, a), of which / is a function. Finally, pH is detennined by the concentration ratio [A ]/[HA], which, for weak acids, and for not too dilute solutions, can be replaced by the stoichiometric ratio, [Na]/[HA], of salt to acid. 

It is possible to estimate, roughly at least, the values of the ionization constants of weak acids and bases by means of potentiometric titration methods. Since the ionization constant K of a weak acid HA is given by... 

Since the terms are constant at a given temperature we may define the ionization constant K by the relation... 

The structures of organic acids as deduced from their ionization constants in aqueous solutions will be developed. The ionization constants K X 10 ) of the acids as calculated from the Ostwald dilution law. 

Hammett equation. One of the first methods for relating structure and reactivity was developed by Hammett (1937). Hammett found that the reactivities of benzoic acid esters were directly related to the ionization constants, K, of the corresponding benzoic acids (Figure 1.3). Using substituted benzoic acids as his standard reference reaction, Hammett developed a LFER in the form ... 

The use of a Hammett substituent constants in QSAR analyses has been prominent since the early studies by Hansch and Fujita (1964) in medicinal chemistry. The electron-withdrawing/releasing potency of substituents on an aromatic system has been formalized by the Hammett equation (Hammett, 1940). The relative reactivities among homologous series of compounds under defined conditions - for example, the logarithms of the rate and equilibrium constants for the hydrolysis of substituted benzoic acid esters (rate constant k) and the ionization constants (K) of the corresponding acids, were found to be linearly related ... 

The OH ion concentration increases until equilibrium is established. Consequently, the H3O+ ion concentration decreases so that the product [H3O+] [OH ] remains equal to the ionization constant, K, of water at the temperature of the solution. Thus, the pH is higher than 7, and the solution is basic. 

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