This document discusses key concepts in electrochemistry including electrode potentials, galvanic cells, and electrolytic cells. It defines electrode potentials as the electric potential arising from the separation of charges in redox half reactions. Standard electrode potentials can be measured versus the standard hydrogen electrode and indicate whether the forward or backward reaction is favored. Electrode potentials are also used to predict the feasibility of redox reactions. The document distinguishes anodes and cathodes in galvanic and electrolytic cells and how to draw cell diagrams. It provides strategies for using calculations involving current, time, moles of electrons, and Faraday's constant to solve electrochemistry problems.

1. Electrochemistry Electrode Potentials

2. Electrochemistry 1. What are electrode potentials?

3. Electrochemistry Electric potential arising from the separation of charges in the equilibrium in a redox half equation. It is measured with respect to S.H.E. Examples : 1. What are electrode potentials? Zn 2+ (aq) + 2e – ⇌ Zn (s) Fe 3+ (aq) + e – ⇌ Fe 2+ (aq) 2H + (aq) + e – ⇌ H 2 (g) Cu 2+ (aq) + 2e – ⇌ Cu (s)

4. Electrochemistry 2. What can we know from electrode potentials?

5. Electrochemistry 2. What can we know from electrode potentials? [Sign] + forward reaction ( reduction ) favoured – backward reaction ( oxidation ) favoured [Magnitude] – the extent the reaction is favoured

6. Electrochemistry 3. How can we measure standard electrode potentials?

7. Electrochemistry connect the half cell that you wish to study to the SHE Note : You need to be know how to draw the cell setup. Things to note when drawing half cell: (1) salt bridge, (2) voltmeter and (3) ensure all gases, solutions are at standard conditions. 3. How can we measure standard electrode potentials?

8. Electrochemistry 4. How can we use standard electrode potentials?

9. Electrochemistry to predict whether a redox reaction is feasible when 2 species are mixed. Examples : 4. How can we use standard electrode potentials? I 2 + Cr 2+  feasible? V 3+ + Cu 2+  feasible?

10. Electrochemistry 4. How can we use standard electrode potentials? Strategy 1. Identify possible oxidation/ reduction reactions Find electrode potentials for these half equations Calculate E cell = E red – E ox E cell + feasible – not feasible

11. Electrochemistry Galvanic Cells

12. Electrochemistry 5. How to distinguish anode and cathode? Galvanic Cell

13. Electrochemistry 5. How to distinguish anode and cathode? Positive  remove electrons  Reduction  Cathode Negative  produce electrons  Oxidation  Anode Electrons flow from A  C Galvanic Cell

14. Electrochemistry 6. How to draw cell diagram?

15. Electrochemistry 6. How to draw cell diagram? Example

16. Electrochemistry 6. How to draw cell diagram? Anode || Cathode 2. Electrodes at the extreme ends. 3. Anode: Fe 2+  Fe 3+ Cathode: H +  H 2 4. If redox species of the same phase, separate by comma; different phase by | Pt (s) | Anode || Cathode | Pt (s) Pt (s) | Fe 2+ Fe 3+ || H + H 2 | Pt (s) Pt(s) | Fe 2+ , Fe 3+ (aq) || H + (aq) | H 2 (g) | Pt(s)

17. Electrochemistry Electrolytic Cells

18. Electrochemistry 7. How to distinguish anode and cathode? Electrolytic Cell

19. Electrochemistry 7. How to distinguish anode and cathode? Positive  attract anions  oxidized  Anode Negative  attract cations  reduced  Cathode Electrons flow from A  C Electrolytic Cell

20. Electrochemistry 8. How to predict what species is discharged? 1. Identify all ions in solution (including H 2 O) Cations attracted to cathode; Anions attracted to anode Find electrode potentials for these half equations E ° Cathode more positive or less negative is discharged Anode more negative or less positive is discharged

21. Electrochemistry Calculations (Strategy) Question will surely involve 1 or more of the formulas: Q = I t = n F I: current (A) n: moles of electrons! t: time ( s ) F: Faradays constant (96500 C/mol) F = Le L: Avogadro’s constant e: 1.6 x 10 –19 C