Bear in mind when several equations is placed into give a 3rd, the latest harmony lingering with the third formula translates to this product of your harmony constants of your first two equations. (Section 15.3)

Thus, the product of K_{a} and K_{b} is the ion-product constant for water, K_{w} (Equation ). We expect this result because adding Equations and gave us the autoionization equilibrium for water, for which the equilibrium constant is K_{w}.

As the strength of an acid increases (K_{a} gets larger), the strength of its conjugate base must decrease (K_{b} gets smaller) so that the product K_{a} ? K_{b} remains 1.0 ? 10 –1cuatro at 25 °C. TABLE 16.5 demonstrates this relationship.

By using Equation , we can calculate K_{b} for any weak base if we know K_{a} for its conjugate acid. Similarly, we can calculate K_{a} for a weak acid if we know K_{b} for its conjugate base. As a practical consequence, ionization constants are often listed for only one member of a conjugate acid–base pair. For example, Appendix D does not contain K_{b} values for the anions of weak acids because they can be readily calculated from the tabulated K_{a} values for their conjugate acids.

If you look up the values for acid-or base-dissociation constants in a chemistry handbook, you may find them expressed as pK_{a} or pK_{b} (that is, –log K_{a} or –log K_{b}) (Section 16.4). Equation can be written in terms of pK_{a} and pK_{b} by taking the negative logarithm of both sides:

Many low-molecular-weight amines have a fishy odor. Amines and NH_{3} are produced by the anaerobic (absence of O_{2}) decomposition of dead animal or plant matter. Two such amines with very disagreeable odors are H_{2}N(CH_{2})_{4}NH_{2}, putrescine, and H_{2}N(CH_{2})_{5}NH_{2}, cadaverine.

Many medications, together with quinine, codeine, caffeine, and amphetamine, try amines. Like many amines, this type of compounds is weak angles; this new amine nitrogen is readily protonated upon medication that have an acid. Brand new resulting items are entitled acidic salts. When we use A since abbreviation having an amine, the fresh new acid sodium molded by reaction with hydrochloric acid would be written AH + Cl – . It’s also composed since the An effective·HCl and also known as an effective hydrochloride. Amphetamine hydrochloride, like, ‘s the acid salt shaped of the treating amphetamine with HCl:

Therefore, of numerous drugs that will be amines are sold and you will administered because acidic salts. A few examples more than-the-stop medication containing amine hydrochlorides because the active ingredients are provided inside Figure .

Analyze We are asked to determine dissociation constants for F – , the conjugate base of HF, and NH_{4} + , the conjugate acid of NH_{3}.

## That it matchmaking is indeed important it should found special attention: The merchandise of your acid-dissociation constant to possess an acid and the legs-dissociation lingering because of its conjugate foot equals the ion-unit lingering for h2o:

Plan We can use the tabulated K values for HF and NH_{3} and the relationship between K_{a} and K_{b} to calculate the ionization constants for their conjugates, F – and NH_{4} + .

(a) For the weak acid HF, Table 16.2 and Appendix D give K_{a} = 6.8 ? 10 –4 . We can use Equation to calculate K_{b} for the conjugate base, F – :

(b) For NH_{3}, Table 16.4 and in Appendix D give K_{b} = 1.8 ? 10 –5 , and this value in Equation gives us K_{a} for the conjugate acid, NH_{4} + :

Check The respective K values for F – and NH_{4} + are listed in Table 16.5, where we see that the values calculated here agree with those in Table 16.5.