Standard Electrode Potentials and Redox Activity

Electrochemistry

Standard Electrode Potentials

Standard electrode potentials (E0) are measured under standard conditions (25°C, 1 M concentration, 1 atm pressure) and indicate the tendency of a species to be reduced. These values are essential for predicting the direction of redox reactions and for calculating cell potentials in electrochemical cells.

• Reduction Half-Reaction: The process in which a species gains electrons.

• Standard Electrode Potential (E0): The voltage associated with a reduction half-reaction at standard conditions, measured relative to the standard hydrogen electrode (SHE), which is assigned a potential of 0.00 V.

• High E0 Value: Indicates a strong tendency to be reduced (good oxidizing agent).

• Low E0 Value: Indicates a strong tendency to be oxidized (good reducing agent).

Interpreting the Table of Standard Electrode Potentials

The table lists various reduction half-reactions and their standard electrode potentials. Species at the top of the table (high E0) are strong oxidizing agents, while those at the bottom (low E0) are strong reducing agents.

Reduction Half-Reaction	E0 (V)
F2(g) + 2e- → 2F-(aq)	2.87
MnO4-(aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(l)	1.51
Cl2(g) + 2e- → 2Cl-(aq)	1.36
Ag+(aq) + e- → Ag(s)	0.80
Cu2+(aq) + 2e- → Cu(s)	0.34
2H+(aq) + 2e- → H2(g)	0.00
Zn2+(aq) + 2e- → Zn(s)	-0.76
Fe2+(aq) + 2e- → Fe(s)	-0.44
Na+(aq) + e- → Na(s)	-2.71
Li+(aq) + e- → Li(s)	-3.04

Additional info: Table entries above are selected for illustration; the full table includes many more half-reactions. The table is organized from highest to lowest E0 values, indicating decreasing oxidizing strength and increasing reducing strength.

Applications of Standard Electrode Potentials

• Predicting Spontaneity: A redox reaction is spontaneous if the cell potential (Ecell) is positive.

• Calculating Cell Potential: The standard cell potential is calculated as: $E_{cell}^0 = E_{cathode}^0 - E_{anode}^0$

• Identifying Oxidizing and Reducing Agents: Species with high E0 values are good oxidizing agents; those with low E0 values are good reducing agents.

Example: Calculating the Standard Cell Potential

Consider a cell with Zn(s) and Cu(s) electrodes:

• Zn2+(aq) + 2e- → Zn(s), $E^0 = -0.76$ V

• Cu2+(aq) + 2e- → Cu(s), $E^0 = 0.34$ V

Cell potential:

$E_{cell}^0 = E_{cathode}^0 - E_{anode}^0 = 0.34 - (-0.76) = 1.10$ V

Summary Table: Oxidizing and Reducing Strength

Position in Table	Agent Type	Strength
Top (High E0)	Oxidizing Agent	Strong
Bottom (Low E0)	Reducing Agent	Strong

Additional info: The table is a key reference for Chapter 20: Electrochemistry, and is used to solve problems involving redox reactions, electrochemical cells, and predicting reaction spontaneity.