Unit 9 Study Guide: Electrochemistry and Thermodynamics

Electrochemistry

The study of the interchange of chemical and electrical energy.

Redox Reaction

A reaction that involves the transfer of electrons, combining reduction and oxidation.

Oxidation

Loss of electrons, resulting in an increase in oxidation number, occurs at the anode.

Reduction

Gain of electrons, resulting in a decrease in oxidation number, occurs at the cathode.

Galvanic Cell

A cell that converts chemical energy from a spontaneous redox reaction into electrical energy.

Electrolytic Cell

A cell that requires an external power source to drive a non-spontaneous reaction.

Anode

The electrode where oxidation occurs; it loses mass over time.

Cathode

The electrode where reduction occurs; it gains mass over time.

Salt Bridge

A pathway that allows the flow of ions to balance charge in a galvanic cell.

Cell Potential ($E_{cell}$)

The voltage capacity of a cell under standard conditions.

Standard Reduction Potentials

Tables providing the potential of half-reactions for calculating cell voltage.

Nernst Equation

An equation that relates cell potential to concentration of reactants and products.

Faraday's Constant ($F$)

The charge of one mole of electrons, approximately 96,485 C/mol.

Gibbs Free Energy ($ΔG^ullet$)

A thermodynamic quantity that indicates the spontaneity of a reaction.

Concentration Cell

A cell that uses identical metals and solutions at different concentrations.

Stoichiometry in Electrolysis

The calculation of quantities of reactants/products based on electron flow.

Current ($I$)

The flow of electric charge, measured in Amperes (A).

Charge ($q$)

The total electric charge transferred, measured in Coulombs (C).

Oxidation Number

A measure of the degree of oxidation of an atom in a compound.

Mnemonics: OIL RIG

Oxidation Is Loss, Reduction Is Gain.

Electrons flow from Anode to Cathode

The direction of electron flow in both galvanic and electrolytic cells.

Qualitative Analysis

Analysis of how concentration affects cell voltage relative to standard conditions.

Equilibrium Condition ($E_{cell} = 0$)

Occurs when the reaction quotient ($Q$) equals the equilibrium constant ($K$).

Water Competing in Electrolysis

Water may be oxidized or reduced based on its reduction/oxidation potential.

Negative Free Energy Units

Understand that ΔG is typically reported in Joules, not Kilojoules.

Common Mistakes in Stoichiometry

Do not multiply voltage by coefficients in balanced redox equations.