Acetic acid, 152 buffer capacity

Thus, a sodium acetate-acetic acid buffer s capacity is maximum when equimolecular concentrations are taken in their mixture the pH becomes 4.74 (for Ka = 1.82 x 10 ). When the ratio salt/acid is varied, the buffer will have a different pH, but not far away from the value of pKa. The maximum variation in the acid salt ratio allowed is 1 10 or 10 1. The limiting values of the buffer pH becomes... 

Exercise 5.4, One liter (1 L) of a buffer solution contains 0.10 mole of acetic acid, HC2H3O2, and 0.10 mole of sodium acetate, NaC2H302. If the acid-dissociation constant for acetic acid is 1.74x10", what is the pH of the solution What is the acid buffering capacity of the solution ... 

Buffer action 46 Buffer capacity 48 Buffer mixture universal, (T) 831 Buffer solutions 46, (T) 831 acetic acid-sodium acetate, 49 for EDTA titrations, 329 preparation of IUPAC standards, 569 Bumping of solutions 101 Buoyancy of air in weighing 77 Burette 84, 257 piston, 87 reader, 85 weight, 86... 

The peak capacity is not pertinent as the separation was developed by a solvent program. The expected efficiency of the column when operated at the optimum velocity would be about 5,500 theoretical plates. This is not a particularly high efficiency and so the separation depended heavily on the phases selected and the gradient employed. The separation was achieved by a complex mixture of ionic and dispersive interactions between the solutes and the stationary phase and ionic, polar and dispersive forces between the solutes and the mobile phase. The initial solvent was a 1% acetic acid and 1 mM tetrabutyl ammonium phosphate buffered to a pH of 2.8. Initially the tetrabutyl ammonium salt would be adsorbed strongly on the reverse phase and thus acted as an adsorbed ion exchanger. During the program, acetonitrile was added to the solvent and initially this increased the dispersive interactions between the solute and the mobile phase. 

With a given weak acid, a buffer soiution can be prepared at any pH within about one unit of its p vaiue. Suppose, for exampie, that a biochemist needs a buffer system to maintain the pH of a soiution ciose to 5.0. What reagents shouid be used According to the previous anaiysis, the weak acid can have a p Z a between 4.0 and 6.0. As the p deviates from the desired pH, however, the soiution has a reduced buffer capacity. Thus, a buffer has maximum capacity when its acid has its p as ciose as possibie to the target pH. Tabie 18-1 iists some acid-base pairs often used as buffer soiutions. For a pH - 5.0 buffer, acetic acid (p Za — 4.75) and its conjugate base, acetate, wouid be a good choice. 

Buffer solutions have two important characteristics. One of these characteristics is the pH of the solution. The other is its buffer capacity the amount of acid or base that can be added before considerable change occurs to the pH. The buffer capacity depends on the concentration of the acid/conjugate base (or the base/conjugate acid) in the buffer solution. When the ratio of the concentration of the buffer components is close to 1, the buffer capacity has reached its maximum. As well, a buffer that is more concentrated resists changes to pH more than than a buffer that is more dilute. This idea is illustrated in Figure 8.10, with buffer solutions of acetic acid and acetate of different concentrations. 

The LDso values for picric acid after oral dosing of male and female rats were 290 and 200 mg/kg, respectively. Death was due to severe acidosis, with toxic doses of picric acid exceeding the buffering capacity of the blood. In rats, metabolism of picric acid is primarily limited to reduction of nitro groups of the aromatic ring and subsequent conjugation by acetate. 

To appreciate the ability of a buffer solution to maintain a nearly constant pH, let s contrast the behavior of the 0.10 M acetic acid-0.10 M sodium acetate buffer with that of a 1.8 X 10 5 M HC1 solution. This very dilute HC1 solution has the same pH (4.74) as the buffer solution, but it doesn t have the capacity to soak up added... 

M NaOH was added to a buffer containing 0.1 M sodium acetate and 0.1 M acetic acid. What is the buffer capacity of the solution ... 

Plot the pH-buffer capacity curve for mixtures of acetic acid and sodium acetate of total concentration 0.2 n. Points should be obtained for mixtures containing 10, 20, 30, 40, 50, 60, 70, 80 and 90 per cent of sodium acetate, the pH s being estimated by the approximate form of the Henderson equation. Plot the buffer capacity curve for water at pH s 1, 2, 3 and 4, and superimpose the result on the curve for acetic acid. 

Utilize the general form of the acetic acid-acetate buffer capacity curve obtained in Problem 11 to draw an approximate curve for the buffer capacity over the range of pH from 2 to 13 of the universal buffer mixture described on page 415. It may be assumed that the total concentration of each acid and its salt is always 0.2 molar. 

Protein thermal stabilities were determined by monitoring the circular dichroism at 223 nm as a function of sample temperature (Eriksson et al., 1993 Zhang et al., 1995). The buffer was 0.1 M sodium chloride, 1.4 mM acetic acid, 8.6 mM sodium acetate, pH 5.42, with protein present at 15 to 30 /tg/ml. The melting temperature, T , of WT was 65.3°C. Free energy values were computed at 59°C assuming a constant change in heat capacity, ACp of 2.5 kcal/mol-deg. 

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