UNIT: 9.9 In-Depth Notes on Cell Potential and Gibbs Free Energy for Galvanic Cells

Cell Potential Overview
- Definition: Cell potential refers to the voltage generated by a galvanic cell during a redox reaction.
- Symbol: Often denoted as ( E{cell} ) or ( E{cell} ).
- Measurement: Measured in volts and can be assessed using a voltmeter.
Galvanic Cells Basics
- Comprised of two half-cells involved in oxidation-reduction (redox) reactions.
- Electrons flow from oxidation (anode) to reduction (cathode).
- Galvanic cells convert chemical energy into electrical energy.

Electromotive Force (EMF): Often synonymous with cell potential, although more accurately represents the potential difference driving electron flow.
Standard Reduction Potentials: A table listing half-reactions with their corresponding potentials under standard conditions.
Favorable Reactions: Reactions which are spontaneous and have positive potentials.

Hydrogen is assigned a standard reduction potential of 0 volts, serving as a reference.
Example: Fluorine gas has a high standard reduction potential of +2.87 volts, making it very favorable for reduction.
Redox reactions are assessed with half-reactions, where reduction half-reactions show electrons on the reactants side.

Oxidation Half-Reaction: Can be obtained by reversing the reduction reaction, leading to a change in sign of the potential.
- Most negative potential in reduction becomes the most positive when flipped for oxidation.
To create a balanced redox equation, combine oxidation and reduction half-reactions, ensuring electron counts are equal.

The total cell potential is calculated as the sum of the oxidation and reduction potentials: [ E{cell} = E{reduction} + E_{oxidation} ]
Always ensure one half-reaction is flipped to match galvanic cell requirements of one oxidation and one reduction.

Relation: The equation relating cell potential ( E ) and Gibbs free energy ( \Delta G ) is given by: [ \Delta G = -nF E_{cell} ]
- Where:
- ( n ): Moles of electrons transferred.
- ( F ): Faraday's constant, a measurable charge.
- Positive cell potential corresponds to a negative ( \Delta G ), indicating spontaneity.

In balanced cell reactions, track the flow of electrons from anode (oxidation) to cathode (reduction).
When presented with galvanic cell diagrams or equations:
- Identify half-reactions and their potentials.
- Determine what needs to be flipped to yield a positive total potential.
- Ensure electron counts balance in the final equation.

A negative ( \Delta G ) implies that the equilibrium constant ( K ) is greater than 1, indicating product favorability.

Understanding galvanic cells involves recognizing how cell potential and Gibbs free energy interact for spontaneous reactions.
Batteries combine multiple galvanic cells in series to achieve higher voltage, suitable for practical applications.