1. Chapter 18: Introduction to Electrochemistry CHE 321: Quantitative Chemical Analysis Dr. Jerome Williams, Ph.D. Saint Leo University

2. Overview Electrochemistry Electrochemical Cells –Oxidation & Reduction –Electrodes Oxidation & Reduction Current, Voltage, & Cell Potential Cell Notation

3. Electrochemistry Electrochemistry is the study of oxidation- reduction (redox) reactions that produce or require an electric current Conversion between chemical energy and electrical energy is carried out in an electrochemical cell

4. Electrochemical Cells Two types of Electrochemical cells Voltaic (Galvanic) cells -spontaneous redox reactions take place Electrolytic cells are where non- spontaneous redox reactions can be made to occur by the addition of electrical energy (process is termed electrolysis)

5. p443

6. Oxidation & Reduction Oxidation is the process that occurs when –oxidation number of an element increases –element loses electrons –compound adds oxygen –compound loses hydrogen –half-reaction has electrons as products Reduction is the process that occurs when –oxidation number of an element decreases –element gains electrons –compound loses oxygen –compound gains hydrogen –half-reactions have electrons as reactants

7. Oxidation–Reduction oxidation and reduction must occur simultaneously –if an atom loses electrons another atom must take them the reactant that reduces an element in another reactant is called the reducing agent –the reducing agent contains the element that is oxidized the reactant that oxidizes an element in another reactant is called the oxidizing agent –the oxidizing agent contains the element that is reduced 2 Na(s) + Cl 2 (g) → 2 Na + Cl – (s) Na is oxidized, Cl is reduced Na is the reducing agent, Cl 2 is the oxidizing agent

8. Electrodes Anode –electrode where oxidation occurs –anions attracted to it –connected to positive end of battery in electrolytic cell –loses weight in electrolytic cell Cathode –electrode where reduction occurs –cations attracted to it –connected to negative end of battery in electrolytic cell –gains weight in electrolytic cell electrode where plating takes place in electroplating

9. Figure 18-2a p447

10. Figure 18-2b p447

11. Figure 18-2c p447

12. Figure 18-4a p453

13. Figure 18-4b p453

14. Figure 18-4c p453

15. Figure 18-5 p455

16. Figure 18-6 p457

17. Figure 18-7 p458

18. Figure 18-8 p459

19. Table 18-1 p464

20. Figure 18-9 p466

21. Figure 18-10 p469

22. Nernst Equation