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Ebook Analytical chemistry (7th edition): Part 2

(BQ) Part 2 book "Analytical chemistry" has contents: Redox and potentiometric titrations; spectrochemical methods; liquid chromatography and electrophoresis; kinetic methods of analysis; automation in measurements;.and other contents. | Christian7e c13.tex V2 - 08/13/2013 1:49 P.M. Page 399 Chapter Thirteen POTENTIOMETRIC ELECTRODES AND POTENTIOMETRY Chapter 13 URLs Learning Objectives WHAT ARE SOME OF THE KEY THINGS WE WILL LEARN FROM THIS CHAPTER? ● Types of electrodes and electrode potentials from the Nernst equation (key equations: 13.3, 13.10, 13.16), pp. 400, 401, 402 ● The pH glass electrode (key equation: 13.42), p. 413 ● Liquid junctions and junction potentials, p. 405 ● Standard buffers and the accuracy of pH measurements, pp. 418 ● Reference electrodes, p. 407 ● The pH meter, p. 421 ● Accuracy of potentiometric measurements (key equation: 13.36), p. 412 ● Ion-selective electrodes, p. 424 ● The selectivity coefficient (key equation: 13.46), p. 428 In Chapter 12, we mentioned measurement of the potential of a solution and described a platinum electrode whose potential was determined by the half-reaction of interest. This was a special case, and there are a number of electrodes available for measuring solution potentials. In this chapter, we list the various types of electrodes that can be used for measuring solution potentials and how to select the proper one for measuring a given analyte. The apparatus for making potentiometric measurements is described along with limitations and accuracies of potentiometric measurements. The important glass pH electrode is described, as well as standard buffers required for its calibration. The various kinds of ion-selective electrodes are discussed. The use of electrodes in potentiometric titrations is described in Chapter 14. Potentiometric electrodes measure activity rather than concentration, a unique feature, and we will use activities in this chapter in describing electrode potentials. An understanding of activity and the factors that affect it are important for direct potentiometric measurements, as in pH or ion-selective electrode measurements. You should, therefore, review the material on activity and activity coefficients .