Base-dissociation constant table

Table 8.3 lists the base dissociation constants for several weak bases at 25°C. Nitrogen-containing compounds are Bronsted-Lowry bases, because the lone pair of electrons on a nitrogen atom can bond with H+ from water. The steps for solving problems that involve weak bases are similar to the steps you learned for solving problems that involve weak acids. 

Kjj is the base dissociation constant, or base ionization constant, that measures a base s strength. Some values are given for bases in Table 3. 

As usual, [H20] is omitted from the equilibrium constant expression. Table 15.4 lists some typical weak bases and gives their Kb values. (The term base-protonation constant might be a more descriptive name for Kb, but the term base-dissociation constant is still widely used.)... 

Base dissociation constants, listed in Table 1.6, are related to the protolysis constant of their conjugate acid through the equation... 

The Henderson-Hasselbalch equation provides a general solution to the quantitative treatment of acid-base equilibria in biological systems. Table 2.4 gives the acid dissociation constants and values for some weak electrolytes of biochemical interest. 

The preparation of a buffer solution of a definite pH is a simple process once the acid (or base) of appropriate dissociation constant is found smhll variations in pH are obtained by variations in the ratios of the acid to the salt concentration. One example is given in Table 2.2. 

If the agent is an acid or a base its degree of ionization will depend on the pH. If its acid dissociation constant,is known, the degree of ionization at any pH may be calculated or determined by reference to published tables. 

TABLE 4.1 DISSOCIATION CONSTANTS FOR COMMON ACIDS AND BASES ... 

The above treatment of moderately dilute acids and dibasic acids can be used for analogous cases of bases. Table 1.7 lists examples of dissociation constants of bases in aqueous solutions. 

Table 1.7 Dissociation constants of weak acids and bases at 25°C. (From CRC Handbook of Chemistry and Physics)... 

Lide, D. R., Ed. (2003). CRC Handbook of Chemistry and Physics, 84th ed. CRC Press, Boca Raton, FL. Extensive tables of dissociation constants for acids and bases are available in this handbook. 

The line-broadening data as a function of pH, typically shown for the W(IV) in Figs. 13 and 14, incorporating the known pKa values (Table II), were fitted in 5 X 5 Kubo-Sack matrices describing the exchange based on the above schemes (6, 57). The experimentally determined chemical shift and linewidth data in the absence of exchange for the aqua oxo, hydroxo oxo, and dioxo species and the pH-dependent species distribution as calculated from the acid dissociation constants for the four systems were all introduced in the different matrices and the spectra were computer simulated. For each set of chosen rate con-... 

VAN AKEN et al. 0) and EDWARDS et al. (2) made clear that two sets of fundamental parameters are useful in describing vapor-liquid equilibria of volatile weak electrolytes, (1) the dissociation constant(s) K of acids, bases and water, and (2) the Henry s constants H of undissociated volatile molecules. A thermodynamic model can be built incorporating the definitions of these parameters and appropriate equations for mass balance and electric neutrality. It is complete if deviations to ideality are taken into account. The basic framework developped by EDWARDS, NEWMAN and PRAUSNITZ (2) (table 1) was used by authors who worked on volatile electrolyte systems the difference among their models are in the choice of parameters and in the representation of deviations to ideality. 

Amino acids are characterized by the presence of adjacent carboxylic (-C0 H) and amino (-NH) functional groups. The equilibrium constant for protonation or dissociation of these groups is a function of their position in the amino acid molecule. Therefore, widely differing acid-base properties of amino acids occur, depending upon the number of functional groups and their relative position in the molecule. The dissociation constants for various amino acids used in this investigation are given in Table I. 

One major drawback of these sulfonate salts is their poor ion conductivity in nonaqueous solvents as compared with other salts. In fact, among all the salts listed in Table 3, LiTf affords the lowest conducting solution. This is believed to be caused by the combination of its low dissociation constant in low dielectric media and its moderate ion mobil-ityi29 3 compared with those of other salts. Serious ion pairing in LiTf-based electrolytes is expected, especially when solvents of low dielectric constant such as ethers are used. ... 

Biguanides usually behave as mono- and di-acid bases, combining with H+ ions to form the conjugate acid, but may also act as acids. The acid dissociation constants of many biguanides have been measured, and are collected in Tables 1 and 2. 

A quantitative measure of the degree of dissociation is given by the equilibrium constant for the acid or base. The higher the equilibrium constant is, the greater the percent dissociation of the acid or base. Therefore, a higher equilibrium constant means a stronger acid or base. Equilibrium constants, K and K, are listed for several com-mon weak acids and bases in Table 13.4. 

There is often a large variation in values from source to source— in some cases, some orders of magnitude. For diis reason, only one significant figure (at most) is given before the exponent. A table of solubility products for many sulphides based on a reevaluated value for the second dissociation constant of H2S is given in Ref. 1. The values in that study are typically some orders of magnitude lower than the ones shown here. 

Bruice and Schmir (3) have shown that for a series of imidazole derivatives, klm depends on the base strength of the catalyst and since pKA is an approximate measure of base strength, the value of klm should increase with increase in pKA. Table I shows that this is indeed the case. Imidazole, pKA = 7.08, has a catalytic constant eight times larger than that of benzimidazole, pKA = 5.53. Bronsted and Guggenheim (2) have obtained a linear relationship between log k/ and pKA for a series of carboxylic acids in the pKA range of 2 to 5, where kB is the carboxvlate anion basic catalytic constant for the mutarotation of glucose and Ka is the acid dissociation constant of the acid. Our results for imidazole and benzimidazole fit fairly well into the Bronsted plot. 

Electrical Conductance of Aqueous Solutions of Ammonia and Metal Hydroxides. Check the electrical conductance of 1 W solutions of sodium hydroxide, potassium hydroxide, and ammonia. Record the ammeter readings. Arrange the studied alkalies in a series according to their activity. Acquaint yourself with the degree of dissociation and the dissociation constants of acids and bases (see Appendix 1, Tables 9 and 10). Why is the term apparent degree of dissociation used to characterize the dissociation of strong electrolytes ... 

The phenanthrolines are di-acidic bases. The two acid dissociation constants, ki and k2, for all the phenanthrolines have been determined. Typical values are recorded in Table I. Thermodynamic data for the equilibria have also been obtained.20,21 117-120... 

The definition of pH is pH = —log[H+] (which will be modified to include activity later). Ka is the equilibrium constant for the dissociation of an acid HA + H20 H30+ + A-. Kb is the base hydrolysis constant for the reaction B + H20 BH+ + OH. When either Ka or Kb is large, the acid or base is said to be strong otherwise, the acid or base is weak. Common strong acids and bases are listed in Table 6-2, which you should memorize. The most common weak acids are carboxylic acids (RC02H), and the most common weak bases are amines (R3N ). Carboxylate anions (RC02) are weak bases, and ammonium ions (R3NH+) are weak acids. Metal cations also are weak acids. For a conjugate acid-base pair in water, Ka- Kb = Kw. For polyprotic acids, we denote the successive acid dissociation constants as Kal, K, K, , or just Aj, K2, A"3, . For polybasic species, we denote successive hydrolysis constants Kbi, Kb2, A"h3, . For a diprotic system, the relations between successive acid and base equilibrium constants are Afa Kb2 — Kw and K.a Kbl = A w. For a triprotic system the relations are A al KM = ATW, K.d2 Kb2 = ATW, and Ka2 Kb, = Kw. 

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