Ch.18 - ElectrochemistryWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Jules Bruno

Within electrochemistry, the Nernst Equation reveals the quantitative connection between the concentrations of compounds and cell potential. 

The Nernst Equation

The Nernst Equation allows us to relate the reduction potential of an electrochemical reaction to the concentration, temperature and standard cell potential of a species. Its equation is: 

Nernst-Equation-CalculatedThe Nernst Equation 

Standard Cell Potential (Eo)

The variable of Eo represents the cell potential under standard state conditions. Standard state conditions are 1.0 M for concentration, 25oC for temperature, pH = 7.0, and 1.0 atmosphere (atm) for pressure. 


Cell Potential (ECell

The variable of ECell represents the cell potential under non-standard conditions. 


Gas Constant (R)

The variable of R represents the gas constant of the gas and is equal to 8.314 when incorporating joules (J) into its units. 

R-ConstantUniversal R Constant

Temperature (T)

The variable of T represents the absolute temperature of the gas. The units are in Kelvin.


Moles of Electrons (n)

The variable of n represents the number of electrons transferred during the oxidation-reduction process within an electrochemical cell. 


Faraday’s Constant (F)

The variable of F represents the number of Coulombs (C) per mole of electron. 

Faradays-Constant-Electron-ChargeFaraday's Constant

Concentrations (A) 

The variable of A represents the activity or concentration of reacting species within an oxidation-reduction reaction of an electrochemical cell. The ratio itself is represented by the reaction quotient (Q). 

Reaction-QuotientConcentrations & the Reaction Quotient

The Nernst Equation & Reaction Quotient 

The cell potential calculated from Nernst equation is the maximum potential at the instant the cell circuit is connected. At 25oC (298.15 K) we can simplify the Nernst Equation as: 

Derived Nernst Equation (Reaction Quotient)The units remaining are Joules per Coulomb, which is equal to volts (V). 


Conversion between ln and log

By multiplying the natural log (ln) by 2.303 we can obtain the log function. 

Nernst-Equation-LogDerived Nernst Equation (Log Function)


The Nernst Equation & Equilibrium 

As an electrochemical cell discharges electricity and current flows, the electrolyte concentrations from both half-cells will change. The effect is that the reaction quotient (Q) will increase, the non-standard cell potential will decrease and the overall electrochemical cell will reach equilibrium. 


Introducing the equilibrium constant K

As the non-standard cell potential approaches zero the variable of K can be incorporated into the formula. 

Derived Nernst Equation (Equilibrium)

Introducing Gibbs Free Energy

Gibbs Free Energy serves as one of the most important variables in our understanding of spontaneity under Chemical Thermodynamics. The relationship it shares with an electrochemical cell is expressed by the formula: 

Gibbs-Free-Energy-Cell-PotentialGibbs Free Energy & Cell Potential


Jules Bruno

Jules felt a void in his life after his English degree from Duke, so he started tutoring in 2007 and got a B.S. in Chemistry from FIU. He’s exceptionally skilled at making concepts dead simple and helping students in covalent bonds of knowledge.