Buffer capacity calculation

The buffer capacity of the pit fluid is equal to the change in alkalinity of the system per unit change of pH. Figure 4-491 shows the buffer intensity (capacity) of a 0.1 M carbonate pit fluid. Calculating the initial buffer capacity of the pit fluid allows for prediction of the pH change upon introduction of live acid and also any addition of buffer, such as sodium bicarbonate, required to neutralize the excess hydrogen ions. 

Buffer capacity is determined by the amounts of weak acid and conjugate base present in the solution. If enough H3 O is added to react completely with the conjugate base, the buffer is destroyed. Likewise, the buffer is destroyed if enough OH is added to consume all of the weak acid. Consequently, buffer capacity depends on the overall concentration as well as the volume of the buffer solution. A buffer solution whose overall concentration is 0.50 M has five times the capacity as an equal volume of a buffer solution whose overall concentration is 0.10 M. Two liters of 0.10 M buffer solution has twice the capacity as one liter of the same buffer solution. Example includes a calculation involving buffer capacity. 

Twenty-three kinetics have been carried out at 25°C for pH values from 8.25 to 11.25. The rate constant, calculated as the average of all the ks, was of 27.2 9.0 mol 1 min. The pH correction according to equation (2) was not perfect, as there was a tendency to obtain higher k values at lower pH values. However, this was specially true for extreme vdues of our pH range, where the buffer capacity of ethanolamine was limited (higher pHs) or the reaction proceeded very slowly (low pHs), impairing the precision of the data. Another factor that might explain the dispersion of the data is lack of precision of pH measurement (no better than 0.02 pH units). 

The equations used to calculate permeability coefficients depend on the design of the in vitro assay to measure the transport of molecules across membrane barriers. It is important to take into account factors such as pH conditions (e.g., pH gradients), buffer capacity, acceptor sink conditions (physical or chemical), any precipitate of the solute in the donor well, presence of cosolvent in the donor compartment, geometry of the compartments, stirring speeds, filter thickness, porosity, pore size, and tortuosity. 

Tam, K. Y. BUFM AKE A computer program to calculate the compositions of buffers of defined buffer capacity and ionic strength for ultra-violet spectrophotometry, Comp. Chem. 23, 415 119 (1999). 

In contrast to the previous calculation, the fluid maintains a near-neutral pH (Fig. 31.3), reflecting the acid-buffering capacity of the calcite. 

These equations allow us to calculate the pH or pOH of the buffer solution knowing Kof the weak acid or base and the concentrations of the conjugate weak acid and its conjugate base. Also, if the desired pH is known, along with K, the ratio of base to acid can be calculated. The more concentrated these species are, the more acid or base can be neutralized and the less the change in buffer pH. This is a measure of the buffer capacity, the ability to resist a change in pH. 

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. 

Although the condition is hypothetical, it can be calculated that if all of the skeletal muscles in the body degraded glycogen to lactic acid at the maximum rate and, if aU of the protons that were produced were transported into the blood, it would exceed the buffering capacity of the blood and the pH would fall dramatically (see below). This could soon result in death. Hence the inhibitory effect of protons... 

Selected entries from Methods in Enzymology [vol, page(s)] Chelation, 238, 74, 76, 297 buffers [for analysis of exocytosis, 221, 132 preparation, 219, 186 modulation of cytosolic buffering capacity with quin2, 221, 159] fluorescence assay, 240, 724-725, 740-742 fluorescence imaging, 225, 531 238, 303-304, 322-325, 334-335 free intracellular levels after bacterial invasion, 236, 482-489 free calcium in solutions for membrane fusion analysis, calculation and control, 221, 149 homeostasis mechanisms, 238, 80 hormonal elevation, 238, 79 inositol phosphate effect on release, 238, 207 determination of cytosolic levels [computer methods, 238, 73-75 with fura-2, 238, 73, 146 with indo-1, 238, 298, 316-317 with quin-2, 238, 297] hormone effects, 238, 79 ionomycin effects, 238, 79 membrane depolarization effects,... 

Notes on the calculation. A full explanation of soil buffer capacity and derivation of the above factors is given by Rowell (1994, pp. 171-172). 

In principle, it would be logical to combine plots of the buffer index curves of each of the buffer components of milk and thus obtain a plot which could be compared with that actually found for milk. It is not difficult, of course, to conclude that the principal buffer components are phosphate, citrate, bicarbonate, and proteins, but quantitative assignment of the buffer capacity to these components proves to be rather difficult. This problem arises primarily from the presence of calcium and magnesium in the system. These alkaline earths are present as free ions as soluble, undissociated complexes with phosphates, citrate, and casein and as colloidal phosphates associated with casein. Thus precise definition of the ionic equilibria in milk becomes rather complicated. It is difficult to obtain ratios for the various physical states of some of the components, even in simple systems. Some concentrations must be calculated from the dissociation constants, whose... 

PROBLEM 16.8 Calculate the change in pH when 0.002 mol of HN03 is added to 0.100 L of a buffer solution that is 0.050 M in HF and 0.100 M in NaF. Does this solution have more or less buffer capacity than the one in Problem 16.7 ... 

A solution of a weak acid and its conjugate base is called a buffer solution because it resists drastic changes in pH. The ability of a buffer solution to absorb small amounts of added H30+ or OH- without a significant change in pH (buffer capacity) increases with increasing amounts of weak acid and conjugate base. The pH of a buffer solution has a value close to the pKa (— log Ka) of the weak acid and can be calculated from the Henderson-Hasselbalch equation ... 

Calculating the pH of a Buffer 248 Dilution of Buffer Solutions 251 Buffer Capacity 251 Alpha Plots 252... 

D. W. King and D. R. Kester, A General Approach for Calculating Polyprotic Acid Specification and Buffer Capacity, J. Chem. Ed., 67, 932 (1990). 

How many mL of 0.45 M NaOH solution should be added to 45 mL of 0.12 M H3PO4 to prepare a buffer of pH 6.8 Calculate the buffer capacity of the buffer solution. 

Calculate the buffer capacity of 0.1 M sodium carbonate and 0.1 sodium bicarbonate. 

Figure 8A. The relationship between 1/NH3 and 1/NH4 in soil solutions differing in pH and buffering capacity. Experimental data are represented by the solid lines broken lines represent calculated data (from Avnimelech and Laher, 1977, with permission).

Fig. 15.4. Titration data from Tuominen (1967) for Cladonia alpestris, depicted as a function of pH versus concentration of added titrant. The closed circles represent forward titration data, while open circles stand for reversed titration data points. The upper curve is a calculated titration curve in pure water. The shaded area denotes the extent of pH buffering capacity exhibited by the lichen, relative to a non-buffering solution of pure water.

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