Presentation on theme: "Slide 1 of 54 CHEMISTRY Ninth Edition GENERAL Principles and Modern Applications Petrucci Harwood Herring Madura Chapter 20: Electrochemistry."— Presentation transcript:
Slide 1 of 54 CHEMISTRY Ninth Edition GENERAL Principles and Modern Applications Petrucci Harwood Herring Madura Chapter 20: Electrochemistry
Slide 2 of 54 Contents 20-1Electrode Potentials and Their Measurement 20-2Standard Electrode Potentials 20-3E cell, ΔG, and K eq 20-4 E cell as a Function of Concentration 20-5Batteries: Producing Electricity Through Chemical Reactions 20-7Electrolysis: Causing Non-spontaneous Reactions to Occur
Slide 3 of 54 20-1 Electrode Potentials and Their Measurement Cu(s) + 2Ag + (aq) Cu 2+ (aq) + 2 Ag(s) Cu(s) + Zn 2+ (aq) No reaction
Slide 4 of 54 An Electrochemical Half Cell Anode Cathode
Slide 6 of 54 Terminology Electromotive force, E cell. The cell voltage or cell potential. Cell diagram. Shows the components of the cell in a symbolic way. Anode (where oxidation occurs) on the left. Cathode (where reduction occurs) on the right. ◦Boundary between phases shown by |. ◦Boundary between half cells (usually a salt bridge) shown by ||.
Slide 7 of 54 Terminology Zn(s) | Zn 2+ (aq) || Cu 2+ (aq) | Cu(s) E cell = 1.103 V
Slide 8 of 54 Terminology Galvanic cells. Produce electricity as a result of spontaneous reactions. Electrolytic cells. Non-spontaneous chemical change driven by electricity. Couple, M|M n+ A pair of species related by a change in number of e -.
Slide 9 of 54 20-2 Standard Electrode Potentials Cell voltages, the potential differences between electrodes, are among the most precise scientific measurements. The potential of an individual electrode is difficult to establish. Arbitrary zero is chosen. The Standard Hydrogen Electrode (SHE)
Slide 10 of 54 Standard Hydrogen Electrode 2 H + (a = 1) + 2 e - H 2 (g, 1 bar) E° = 0 V Pt|H 2 (g, 1 bar)|H + (a = 1)
Slide 11 of 54 Standard Electrode Potential, E° E° defined by international agreement. The tendency for a reduction process to occur at an electrode. All ionic species present at a=1 (approximately 1 M). All gases are at 1 bar (approximately 1 atm). Where no metallic substance is indicated, the potential is established on an inert metallic electrode (ex. Pt).
Slide 12 of 54 Reduction Couples Cu 2+ (1M) + 2 e - → Cu(s)E° Cu 2+ /Cu = ? Pt|H 2 (g, 1 bar)|H + (a = 1) || Cu 2+ (1 M)|Cu(s) E° cell = 0.340 V Standard cell potential: the potential difference of a cell formed from two standard electrodes. E° cell = E° cathode - E° anode cathodeanode
Slide 13 of 54 Standard Cell Potential Pt|H 2 (g, 1 bar)|H + (a = 1) || Cu 2+ (1 M)|Cu(s) E° cell = 0.340 V E° cell = E° cathode - E° anode E° cell = E° Cu 2+ /Cu - E° H + /H 2 0.340 V = E° Cu 2+ /Cu - 0 V E° Cu 2+ /Cu = +0.340 V H 2 (g, 1 atm) + Cu 2+ (1 M) → H + (1 M) + Cu(s) E° cell = 0.340 V
Slide 14 of 54 Measuring Standard Reduction Potential anode cathode