PH changes

Other important effects of ligand and pH changes on redox potentials will be given under the appropriate element. 

Note that dinitrogen oxide is the other product. In alkaline solution, however, hydroxylamine oxidises iron(II) hydroxide to iron(III) hydroxide and is itself reduced to ammonia. This is an example of the effect of pH change on oxidation-reduction behaviour (p. 101). ... 

Suppose that the only available indicator changes color at a pH of 6.8. Is this end point close enough to the equivalence point that the titration error may be safely ignored To answer this question we need to know how the pH changes during the titration. 

In the overview to this chapter we noted that the experimentally determined end point should coincide with the titration s equivalence point. For an acid-base titration, the equivalence point is characterized by a pH level that is a function of the acid-base strengths and concentrations of the analyte and titrant. The pH at the end point, however, may or may not correspond to the pH at the equivalence point. To understand the relationship between end points and equivalence points we must know how the pH changes during a titration. In this section we will learn how to construct titration curves for several important types of acid-base titrations. Our... 

Boiler feed-water systems that use dernineralized or evaporated makeup or pure condensate may be protected from caustic attack through coordinated phosphate and pH control. Phosphate buffers the boiler water, reducing the chance of large pH changes due to the development of high caustic or acid concentrations. Excess caustic combines with disodium phosphate and forms trisodium phosphate. Sufficient disodium phosphate must be available to combine with all of the free caustic in order to form trisodium phosphate. 

Comparison of electronic absorption spectra of BPR and PR in solution with electronic absolution spectra of BPR and PR on NH -S and en-S surfaces has been made. In contrast to aqueous solutions, where shift of the absolution maximum of dyes is occurred when pH is changed, significant shift of maxima is not observed on aminosilica gels surface during pH changing. Both reagents BPR and PR have an absolution maximum in the field of 17900-18100 cm at different pH values. However use of BPR is more preferable than that of PR as qualitative soi ption of BPR occurs at wider pH range. 

C shifts respond to pH changes with even greater sensitivity this is demonstrated by the values of pyridine (39b) and its cation (39a). 

Land pollution Gross amenity damage Undermining of site stability Sterilization of surrounding land due to heavy metals pH changes etc. Permanent land contamination ... 

Sissons, C. H., and Cutress, T. W. (1987). In-vitro urea-dependent pH-changes by human salivary bacteria and dispersed, artificial-mouth, bacterial plaques. Arch. Oral Biol. 32, 181-189. 

FIGURE 2.12 The titration curve for acetic acid. Note that the titration curve is relatively flat at pH values near the pK in other words, the pH changes relatively little as OH is added in this region of the titration curve. 

FIGURE 22.27 Light-induced pH changes in chloroplast compartments. Illumination of chloroplasts leads to proton pumping and pH changes in the chloroplast, such that the pH within the thylakoid space falls and the pH of the stroma rises. These pH changes modulate the activity of key Calvin cycle enzymes. 

As discussed in Section 22.7, illumination of chloroplasts leads to light-driven pumping of protons into the thylakoid lumen, which causes pH changes in both the stroma and the thylakoid lumen (Figure 22.27). The stromal pH rises, typically to pH 8. Because rubisco and rubisco activase are more active at pH 8, COg fixation is activated as stromal pH rises. Fructose-1,6-bisphosphatase, ribulose-5-phosphate kinase, and glyceraldehyde-3-phosphate dehydrogenase all have alkaline pH optima. Thus, their activities increase as a result of the light-induced pH increase in the stroma. 

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. 

---