Conjugate acid-base pair defined

In the process of a weak acid or weak base neutralization titration, a mixture of a conjugate acid-base pair exists in the reaction flask in the time period of the experiment leading up to the inflection point. For example, during the titration of acetic acid with sodium hydroxide, a mixture of acetic acid and acetate ion exists in the reaction flask prior to the inflection point. In that portion of the titration curve, the pH of the solution does not change appreciably, even upon the addition of more sodium hydroxide. Thus this solution is a buffer solution, as we defined it at the beginning of this section. 

Table 5.1 gives commonly used examples of conjugate acid-base pair combinations and the pH range for which each is useful. This range corresponds to the pH range defined by the buffer region in the titration curve for each, and the middle of the range corresponds to the midpoint of each titration. 

Define buffer solution, conjugate acid, conjugate base, conjugate acid-base pair, buffer capacity, and buffer region. 

The extent to which the pH of a solution is buffered against additions or removals of protons is measured by the solution s pH buffer capacity. This is defined as the amount of strong acid or base required to produce unit change in pH. The buffering depends on the transfer of protons between donors and acceptors, i.e. Bronsted acids and bases, which form conjugate acid-base pairs. The pH buffer capacity of a solution is calculated from the buffer capacities of the individual acid-base pairs present. 

Acids may be defined as proton donors and bases as proton acceptors. A proton donor and its corresponding proton acceptor make up a conjugate acid-base pair (Fig. 2-16). Acetic acid (CH3COOH), a proton donor, and the acetate anion (CII.COO ), the corre-... 

Such an equilibrium system is termed a conjugate (or corresponding) acid-base system. A and B are termed a conjugate acid-base pair. It is important to realize that the symbol H+ in this definition represents the bare proton (unsolvated hydrogen ion), and hence the new definition is in no way connected to any solvent. The equation expresses a hypothetical scheme for defining the acid and base - it can be regarded as a half reaction which takes place only if the proton, released by the acid, is taken up by another base. 

Define a conjugate acid-base pair, and give an example. 

Confidence limits The values that define the confidence interval. Conjugate acid/base pairs Species that differ from one another by one proton. 

Use Bronsted-Lowry terminology to define the following terms. Illustrate each with a specific example, (a) acid (b) conjugate base (c) base (d) conjugate acid (e) conjugate acid-base pair. 

Arrhenius in 1887 was the first person to give a definition of an acid and a base. According to him, an acid is one that gives rise to excess of in aqueous solution, whereas a base gives rise to excess of OH in solution. This was modified by Bronsted-Lowry in 1923 such that a proton donor was defined as an acid and a proton acceptor as a base. They also introduced the familiar concept of the conjugate acid-base pair. The final refinement to the acid-base theory was completed by Lewis in 1923, who extended the concept that acid is an acceptor of electron pairs while base is a donor of electron pairs. 

An extension of the Brpnsted definition of acids and bases is the concept of the conjugate acid-base pair, which can be defined as an acid and its conjugate base or a base and its conjugate acid. The conjugate base of a Brpnsted acid is the species that remains when one proton has been removed from the acid. Conversely, a conjugate acid results from the addition of a proton to a Brpnsted base. 

Define and identify Brpnsted-Lowry acids and bases and identify conjugate acid-base pairs. (Section 16.2)... 

The values of and for a number of common conjugate acid-base pairs are shown in Table 11.5. Because and values can range over many orders of magnitude, they are often expressed on a logarithmic scale similar to pH. We define pK and pK as follows ... 

Define and identify conjugate acid-base pairs. 

In Chapter 13, conjugate acid-base pairs were defined HA is the conjugate acid of A, and A" is the conjugate base of HA. A simple relation between the acidic and basic ionization constants in a conjugate pair was established (page 251) KJi.ty = Ky,. Thus, if we know the ionization constant for an acid or base, we can find the ionization constant for its conjugate base or acid. 

As a result of the reaction, an acid is transformed into a base, and vice versa. This defines the existence of conjugate acid-base pairs Ai/Bi, A2/B2 like NHj/NHs. 

The theory proposed by Brpnstcd (1923) defines an acid as any substance that can ionize in solution to give a solvated hydrogen ion (i.e. a proton stabilized by interaction with either the solvent or a substance in solution). Conversely a base is a substance which can accept a hydrogen ion. Thus an acid is a proton donor and a base a proton acceptor and the ionization process always involves the two which are known as conjugate acid-base pairs. This concept may be generalized by the equation... 

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