This is an educational resource based on the Wikipedia article on Electrochemistry. Read the source article here. (opens in new tab)

Electrochemistry: The Science of Chemical Reactions and Electricity

An exploration of the fundamental relationship between electrical potential difference and chemical change, covering historical milestones, core principles, and diverse applications.

What is Electrochemistry? ๐Ÿ‘‡ Explore Applications ๐Ÿ’ก

Dive in with Flashcard Learning!


When you are ready...
๐ŸŽฎ Play the Wiki2Web Clarity Challenge Game๐ŸŽฎ

Introduction

Defining Electrochemistry

Electrochemistry is a specialized branch of physical chemistry focused on the interplay between electrical potential differences and identifiable chemical changes. It investigates phenomena where chemical reactions drive electrical potential or are driven by it.

Core Mechanism

At its heart, electrochemistry involves the transfer of electrons. This transfer occurs via an electronically conducting phase, typically an external electric circuit connecting two electrodes. These electrodes are separated by an ionically conducting, electronically insulating electrolyte.

Key Processes

The field encompasses reactions driven by electrical potential (like electrolysis) and those generating potential from chemical reactions (like in batteries and fuel cells). These are collectively termed electrochemical reactions.

Historical Development

Early Discoveries (16th-18th Century)

Interest began in the 16th century with figures like William Gilbert. Otto von Guericke created the first electric generator in 1663. Charles du Fay identified two types of electricity, while Charles-Augustin de Coulomb formulated his law of electrostatic attraction.

  • Luigi Galvani (late 1780s): Observed muscle contractions in frog legs upon contact with metals, proposing "animal electricity".
  • Alessandro Volta (c. 1791): Disputed Galvani's theory, attributing the effect to dissimilar metals. Developed the first practical battery, the Voltaic pile.

The Voltaic Era (19th Century)

The 19th century saw rapid advancements. William Nicholson and Johann Wilhelm Ritter electrolyzed water and discovered electroplating. Humphry Davy isolated reactive metals via electrolysis. Hans Christian ร˜rsted discovered electromagnetism, and Andrรฉ-Marie Ampรจre formalized its mathematical principles.

  • Michael Faraday: Formulated the fundamental laws of electrochemistry and coined key terms.
  • Georg Ohm: Defined Ohm's Law relating voltage, current, and resistance.
  • Svante Arrhenius: Proposed the theory of ionic dissociation in electrolytes (1884).
  • Walther Nernst: Developed the Nernst equation relating cell potential to concentration.
  • Hall-Hรฉroult Process (1886): Enabled industrial production of aluminum via electrolysis.

Modern Developments (20th Century)

The 20th century focused on refining theories and expanding applications. Robert Millikan precisely measured the electron's charge. Johannes Brรธnsted and Martin Lowry developed acid-base theory. Arne Tiselius advanced electrophoresis techniques.

  • 1902: Founding of The Electrochemical Society (ECS).
  • 1923: Brรธnsted-Lowry acid-base theory established.
  • 1937: Arne Tiselius develops sophisticated electrophoresis apparatus.
  • 1949: Founding of the International Society of Electrochemistry (ISE).
  • 1960s-70s: Development of Quantum Electrochemistry.

Core Principles

Redox Reactions

Electrochemistry fundamentally relies on Redox (reduction-oxidation) reactions, involving the transfer of electrons. Oxidation is the loss of electrons (increase in oxidation state), while Reduction is the gain of electrons (decrease in oxidation state). These processes always occur simultaneously.

Common mnemonics include:

  • OIL RIG: Oxidation Is Loss, Reduction Is Gain.
  • LEO the lion says GER: Lose Electrons: Oxidation, Gain Electrons: Reduction.

The species that loses electrons is the reducing agent (reductant), and the species that gains electrons is the oxidizing agent (oxidant).

Balancing Redox Reactions

Balancing redox reactions ensures conservation of mass and charge. The ion-electron method is commonly used, especially in aqueous solutions, involving balancing half-reactions for oxidation and reduction separately.

Acidic Medium: Balance oxygen with H2O and hydrogen with H+ ions.

Basic Medium: Balance oxygen with H2O and hydrogen with OH- ions (or balance as in acidic medium, then neutralize H+ with OH-).

Neutral Medium: Typically balanced using methods similar to acidic conditions.

Example (Acidic): Mn2+ + NaBiO3 โ†’ Bi3+ + MnO4-

Oxidation
4 H2O + Mn2+ โ†’ MnO4- + 8 H+ + 5 e-
Reduction
2 e- + 6 H+ + BiO3- โ†’ Bi3+ + 3 H2O

After balancing electrons and summing half-reactions, the overall balanced equation is obtained.

Electrochemical Cells

These devices convert chemical energy to electrical energy (Galvanic/Voltaic cells) or vice versa (Electrolytic cells). They consist of two electrodes (anode for oxidation, cathode for reduction) immersed in an electrolyte, connected externally for electron flow and internally via an electrolyte bridge for ion flow.

  • Anode: Electrode where oxidation occurs.
  • Cathode: Electrode where reduction occurs.
  • Electrolyte: Conducts ions between electrodes.
  • Salt Bridge/Porous Plug: Completes the circuit by allowing ion migration.
  • Galvanic/Voltaic Cell: Spontaneous redox reaction generates electricity (e.g., batteries).
  • Electrolytic Cell: External voltage drives a non-spontaneous reaction (e.g., electrolysis).

Electrochemical Cells

Galvanic Cells

These cells generate electricity from spontaneous redox reactions. The potential difference (emf) arises from the difference in electrode potentials. A classic example is the Daniell cell (Zn/Zn2+ || Cu2+/Cu).

Cell Diagram: Zn(s) | Zn2+ (1 M) || Cu2+ (1 M) | Cu(s)

Half-Reactions:

Anode (Oxidation)
Zn(s) โ†’ Zn2+(aq) + 2 e-
Cathode (Reduction)
Cu2+(aq) + 2 e- โ†’ Cu(s)

Overall Reaction: Zn(s) + Cu2+(aq) โ†’ Zn2+(aq) + Cu(s)

The standard cell potential (Eยฐcell) is calculated as Eยฐcathode - Eยฐanode.

Standard Electrode Potential

Standard electrode potentials (reduction potentials) are tabulated relative to the Standard Hydrogen Electrode (SHE), which has a potential of 0 V. These values predict the direction and voltage of spontaneous reactions under standard conditions (1 M concentration, 1 atm pressure, 25ยฐC).

Standard Hydrogen Electrode (SHE): 2 H+(aq) + 2 e- โ‡Œ H2(g)

Cell Potential Calculation: Eยฐcell = Eยฐred(cathode) - Eยฐred(anode)

A positive Eยฐcell indicates a spontaneous reaction.

Nernst Equation

The Nernst equation relates cell potential (E) to non-standard conditions (concentrations, temperature). It's crucial for understanding how reactant concentrations affect cell voltage and spontaneity.

The equation is: ฮ”E = ฮ”Eยฐ - (RT / nF) * ln(Q)

Where:

  • ฮ”E = Cell potential under non-standard conditions
  • ฮ”Eยฐ = Standard cell potential
  • R = Gas constant (8.314 J/(Kยทmol))
  • T = Temperature in Kelvin
  • n = Number of moles of electrons transferred
  • F = Faraday's constant (96485 C/mol)
  • Q = Reaction quotient

At 25ยฐC (298 K), it simplifies to: ฮ”E = ฮ”Eยฐ - (0.05916 V / n) * log(Q)

Concentration Cells: A special case where Eยฐ=0, and the cell potential depends solely on concentration differences, driving ion flow from high to low concentration.

Batteries

Powering Devices

Batteries are practical applications of galvanic cells, converting stored chemical energy into electrical energy. Early wet cells powered telegraphs, while dry cells made portable devices feasible. Rechargeable batteries (secondary cells) allow energy interchangeability.

Lead-Acid and Beyond

The lead-acid battery, the first practical rechargeable type, is still vital in automotive applications. Limitations due to water-based electrolytes (freezing, voltage limits) led to advancements like lithium-ion batteries, essential for modern electronics.

  • Lead-Acid: Robust, rechargeable, used in vehicles.
  • Lithium-ion: High energy density, rechargeable, powers portable electronics and EVs.
  • Flow Batteries: Offer large capacity by replenishing reactants externally.
  • Fuel Cells: Convert chemical fuels (like hydrogen) directly to electricity efficiently.

Corrosion

An Electrochemical Process

Corrosion, like rust formation on iron, is an electrochemical process. It occurs when different regions of a metal surface act as anodes (oxidation/corrosion) and cathodes (reduction) in the presence of an electrolyte (like water).

Iron Corrosion Example:

Anode (Oxidation)
Fe(s) โ†’ Fe2+(aq) + 2 e-
Cathode (Reduction, acidic medium)
O2(g) + 4 H+(aq) + 4 e- โ†’ 2 H2O(l)

Fe2+ further oxidizes to form iron(III) oxide hydrate (rust): 4 Fe2+(aq) + O2(g) + (4+2x) H2O(l) โ†’ 2 Fe2O3ยทxH2O(s) + 8 H+(aq)

Corrosion is accelerated by electrolytes like salt water.

Prevention Strategies

Corrosion can be prevented by isolating the metal from the electrolyte (e.g., coatings like paint) or by making the metal the cathode in an electrochemical cell.

  • Protective Coatings: Paint, lacquer, or plating prevents contact with air and moisture. Scratches can expose the metal, leading to localized corrosion.
  • Sacrificial Anodes: Attaching a more reactive metal (like zinc or magnesium) forces the protected metal (e.g., steel hull, pipeline) to become cathodic. The sacrificial metal corrodes instead, requiring periodic replacement.

Electrolysis

Driving Reactions

Electrolysis uses an external electrical source to drive non-spontaneous redox reactions. This occurs in an electrolytic cell, where applied voltage forces electron transfer.

Industrial Processes

Key industrial applications include the production of reactive metals and chemicals.

  • Molten NaCl Electrolysis (Downs Cell): Produces metallic sodium and chlorine gas. Requires ~4V, but higher voltages drive the reaction faster. Half-reactions: Cathode: Na+ + e- โ†’ Na(l); Anode: 2 Cl- โ†’ Cl2(g) + 2 e-.
  • Water Electrolysis: Splits water into hydrogen and oxygen gas using inert electrodes (often platinum). Requires significant voltage (~2V) and an electrolyte (e.g., H2SO4). Half-reactions: Cathode: 2 H2O + 2 e- โ†’ H2(g) + 2 OH-; Anode: 2 H2O โ†’ O2(g) + 4 H+ + 4 e-.
  • Aqueous NaCl Electrolysis (Chloralkali Process): Produces hydrogen gas at the cathode and chlorine gas at the anode, with sodium hydroxide in solution. Water reduction is favored over sodium ion reduction. Overpotential effects can influence reaction rates.

Faraday's Laws

First Law

Quantifies the relationship between the amount of substance produced at an electrode and the quantity of electricity passed through the cell. The mass deposited (m) is proportional to charge (Q), molar mass (M), and inversely proportional to the number of electrons per ion (n) and Faraday's constant (F).

Equation: m = (1/F) โ‹… (QM / n)

Second Law

States that the amounts of different substances deposited by the same quantity of electricity are proportional to their equivalent weights. This principle underpins applications like electroplating.

Concept: Equal quantities of electricity deposit equivalent amounts of substances.

Electroplating uses electrolysis to deposit a thin layer of one metal onto another, often for protection (corrosion resistance) or aesthetics. Faraday's laws help calculate the precise amount of metal to deposit for a desired coating thickness.

Applications

Energy Storage & Conversion

Batteries (primary and secondary), fuel cells, and super-capacitors are major electrochemical technologies for energy storage and conversion.

Industrial Production

Electrolysis is vital for producing metals like aluminum, sodium, and magnesium, as well as chemicals like chlorine and sodium hydroxide (Chloralkali process).

Analysis & Sensing

Electrochemical methods are used in sensors (e.g., glucose meters, breathalyzers), analytical techniques (titrations, voltammetry), and material characterization.

Corrosion Control

Understanding electrochemical principles is key to preventing and mitigating corrosion in structures, pipelines, and vehicles.

Surface Finishing

Electroplating, electro-polishing, and anodizing use electrochemical processes to modify metal surfaces for protection, appearance, or functionality.

Teacher's Corner

Edit and Print this course in the Wiki2Web Teacher Studio

Edit and Print Materials from this study in the wiki2web studio
Click here to open the "Electrochemistry" Wiki2Web Studio curriculum kit

Use the free Wiki2web Studio to generate printable flashcards, worksheets, exams, and export your materials as a web page or an interactive game.

True or False?

Test Your Knowledge!

Gamer's Corner

Are you ready for the Wiki2Web Clarity Challenge?

Learn about electrochemistry while playing the wiki2web Clarity Challenge game.
Unlock the mystery image and prove your knowledge by earning trophies. This simple game is addictively fun and is a great way to learn!

Play now

Explore More Topics

Discover other topics to study!

                                        

References

References

  1.  Frederick Collier Bakewell Electric science; its history, phenomena, and applications, Ingram, Cooke (1853) pp. 27รขย€ย“31
  2.  Charles Knight (ed.) Biography: or, Third division of "The English encyclopedia", Volume 2, Bradbury, Evans & Co. (1867)
  3.  The Nobel Prize in Chemistry 1948 Arne Tiselius, nobelprize.org
  4.  Faraday, Michael (1791รขย€ย“1867), Wolfram Research
  5.  "What is Electropolishing?" https://www.electro-glo.com/what-is-electropolishing/
A full list of references for this article are available at the Electrochemistry Wikipedia page

Feedback & Support

To report an issue with this page, or to find out ways to support the mission, please click here.

Disclaimer

Important Notice

This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is derived from publicly available data and may not be exhaustive or fully up-to-date.

This is not professional advice. The information provided is not a substitute for expert consultation in chemistry, engineering, or any related field. Always consult official documentation and qualified professionals for specific applications or safety-critical information.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.