University:
Santa Ana College
Course:
CHEM 229 | General Chemistry and Qualitative Analysis
Academic year:

2021
Views:

392

Pages:

2
Author:

Alexandria Skinner

Electrochemistry Study Guide 1. Terms to know: • • Electrode Potential/Voltage: The amount of energy per unit of charge that a half-reaction either requires or releases (typically in units of Volts) Standard Hydrogen Electrode (SHE): A platinum electrode that provides a surface for the following reaction: 2H+(aq) (1M) + 2e- -> H2(g) (1 bar) This electrode is arbitrarily assigned a potential of 0. • • Standard Electrode Potential/Voltage: The potential of an electrode in comparison with the SHE. Standard Cell potential/Voltage: The difference in standard potential between the cathode and the anode of an electrochemical cell: E°cell = E°anode – E°cathode 2. How to calculate the Standard Cell Potential for a redox reaction: Take the following reaction: Zn(s) + Cl2(g) -> ZnCl2(aq) a. • • • Assign oxidation numbers: Zn(s) = 0 Cl2(g) = 0 ZnCl2:  Cl = -1  Zn = +2 b. Write oxidation and reduction half-reactions: Red: Cl2(g) + 2e- -> 2Cl-(aq) Ox: Zn(s) -> Zn2+(aq) + 2e- c. Look up standard reduction potentials in a reference table: Cl2(g) + 2e- -> 2Cl-(aq) E° = +1.358V Zn(s) -> Zn2+(aq) + 2e- E° = -0.763V d. Calculate Cell potential using the cell potential equation: E°cell = E°anode – E°cathode E°cell = 1.358 – (-0.763) E°cell = 2.121V Notice that the standard cell potentials in the reference table are all reduction potentials, even though you have one reduction half-reaction and one oxidation half-reaction. This is just convention. Generally, the more positive a reduction potential is, the more spontaneous the reduction reaction, so it makes sense that we get negative reduction potentials for your oxidation half-reactions.

Study Guide for Electrochemistry 1

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