PH calculations

Butler, J. N. Solubility and pH Calculations. Addison-Wesley Reading, MA, 1973. 

The absolute (a) and relative (b) amounts of Pu(IV) hydroxide ion concentration (or pH), calculated by Equation 4 based on the data given in Table I. The region of interest for the present investigation is marked by dotted lines. 

Suppose we are titrating the triprotic acid H P04 with a solution of NaOH. The experimentally determined pH curve is shown in Fig. 11.13. Notice that there are three stoichiometric points (B, D, and F) and three buffer regions (A, C, and E). In pH calculations for these systems, we assume that, as we add the hydroxide solution, initially NaOH reacts completely with the acid to form the diprotic conjugate base... 

A flow chart summarizes the major species in solution and the pH calculations for the four key regions of a weak acid titration curve. 

C18-0136. A technician accidentally pours 35 mL of 12 M HCI into the I.O L of buffer solution freshly prepared as described in Problem 18.93. (a) Do a calculation to determine whether the buffer has been ruined, (b) Is it possible to bring the buffer solution back to the original pH calculated in Problem 18.93 If so, what reagent, and how much, must be added to restore the buffer ... 

If serum protein or surfactant is added to the acceptor wells, then, in general, p[A l> and P r> are not the same, even under iso-pH conditions. The acceptor-to-donor permeability needs to be solved by performing a separate iso-pH assay, where the serum protein or surfactant is added to the donor side, instead of the acceptor side. The value of Pe is determined, using Eq. (7.20), and used in gradient-pH cases in place of P A /) , as described in the preceding section. The gradient-pH calculation procedure is iterative as well. 

Fig. 1. Distribution of mononuclear species as a function of pH calculated from equilibrium constants (pertaining to ionic strength 1.0) given in Table I.

Fig. 2. Distribution of vanadium(V) species as a function of pH, calculated from constants in Table II. Vanadium(V) concentration 0.001 M and ionic medium 0.6 M NaCl.

Fig. 9. Distribution of mononuclear molybdenum(VI) species as a function of the pH calculated from constants given in Table V.

Fig. 5. Apparent pH calculated through distributions of Fe(OH)2+/ Fe3+ (blue diamonds) and Fe(0H) Fe(0H)3 (brown squares), versus the -log[H+] computed from the number of protons added to the solution on the acid side, or from the amount of added hydroxide, taking Kw=14, on the base side.

Figure 9-1 shows the pH calculated for different concentrations of strong base or strong acid in water. There are three regions ... 

The pH calculations are similar to those for corresponding points in the titration of a monobasic compound. Let s examine points A through E in Figure 11 -4. 

For mote about equilibrium calculations, see W. B. Guenther, Unified Equilibrium Calculations (New York Wiley, 1991) J. N. Butler. Ionic Equilibrium Solubility and pH Calculations (New York Wiley, 1998) and M. Meloun, Computation of Solution Equilibria (New York Wiley, 1988). For equilibrium calculation software, see http //www.micromath.com/ and http //www.acadsoft.co.uk/... 

Diffusion coefficients for different initial pH calculated from data obtained by the finite bath technique compare reasonably well with those determined by the infinite bath technique, as can be seen from the data in Table I. The calculated rate curves fit the experimental data very well for initial pH values of 3.50 and 3.70, but for an initial pH of 4.00,... 

The next step, which is representative of all pH calculations, is to find the pH and the accompanying changes in dissolved carbonate species when the water comes to equilibrium with the atmosphere with respect to Pco2- As C02 is lost, the pH will rise. 

We ve seen on numerous occasions that the neutralization reaction of an acid with a base produces water and a salt. But to what extent does a neutralization reaction go to completion We must answer that question before we can make pH calculations on mixtures of acids and bases. Let s look at four types of neutralization reactions (1) strong acid-strong base, (2) weak acid-strong base, (3) strong acid-weak base, and (4) weak acid-weak base. 

Sample results for pH calculations at other places beyond the equivalence point are also included in Table 16.1. 

The results of pH calculations for the titration of 0.100 M CH3C02H with 0.100 M NaOH are plotted in Figure 16.7. Comparison of the titration curves for the weak acid-strong base titration and the strong acid-strong base case shows several significant differences ... 

Figure 16.9 shows the pH titration curve for a typical weak base-strong acid titration, the titration of 40.0 mL of 0.100 M NH3 with 0.100 M HC1. The pH calculations are simply outlined to save space you should verify the results yourself. 

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