Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → General chemistry → Electrochemistry → Introduction to Chemistry ↓


Electrolysis


Electrolysis is an important process in the field of electrochemistry. It involves the use of electrical energy to drive a chemical reaction that would not naturally occur on its own. This process is fundamental in various industrial applications, including the production of chemicals, electroplating, and the extraction of metals. In this detailed discussion, we will discuss the principles of electrolysis, its applications, and the detailed functioning involving various substances.

What is electrolysis?

Electrolysis is a technique that uses an external voltage (electric current) to stimulate a non-spontaneous chemical reaction. This process takes place in a medium that can conduct electricity, known as an electrolyte, usually a liquid containing ions.

Fundamentals of electrolysis

The principle of electrolysis is based on the electrochemical cell. An electrochemical cell has two electrodes: an anode (positive) and a cathode (negative). These electrodes are usually made of inert materials such as platinum or graphite. The electrolyte is the medium through which the ions move during the electrolysis process.

      Anode(+) <---- electrolyte ----> cathode(-)
      positive negative
      Electrode Electrode

How electrolysis works

When electricity passes through the electrolyte, it moves ions toward the electrodes, where reduction and oxidation reactions take place.

  • Anode reaction: Oxidation occurs at the anode. This is where electrons are lost.

    • A - → A + e -

  • Cathode reaction: Reduction takes place at the cathode. Electrons are obtained here.

    • C + e - → C -

The overall process can be summarized by the movement of cations toward the cathode and anions toward the anode. Electrochemical reactions occur at the electrodes, completing the circuit and maintaining the flow of electrons through the outer wire.

Understanding electrolysis through examples

To understand electrolysis in more depth, let's look at some specific examples:

Example 1: Electrolysis of water

The electrolysis of water is a popular example. Here, water is decomposed into oxygen and hydrogen gases. For this reaction to occur, a small amount of electrolyte (such as sulfuric acid) is added to the water to improve electrical conductivity.

      2 H 2 O(l) → 2 H 2 (g) + O 2 (g)
  • Anode (oxidation): Water loses electrons to form oxygen.

    • 2 H 2 O(l) → O 2 (g) + 4 H + + 4 e -

  • Cathode (reduction): Hydrogen ions accept electrons to form hydrogen.

    • 4 H + + 4 e - → 2 H 2 (g)

Example 2: Electrolysis of molten sodium chloride (NaCl)

This process is often used to extract sodium and chlorine. When melted, sodium chloride dissociates into sodium (Na +) and chloride ( Cl− ) ions.

      2 NaCl(l) → 2 Na(s) + Cl 2 (g)
  • Anode (oxidation): Chloride ions lose electrons to form chlorine gas.

    • 2 Cl - → Cl 2 (g) + 2 e -

  • Cathode (reduction): Sodium ions gain electrons to form sodium metal.

    • 2 Na + + 2 e - → 2 Na(s)

Applications of electrolysis

Electrolysis has many practical applications, some of which are detailed below:

1. Electroplating

Electroplating uses electrolysis to cover an object with a thin layer of metal. This can improve corrosion resistance, aesthetic appeal, and reduce costs by using less expensive metals. For example, electroplating silver on a brass object involves using that object as a cathode in a silver nitrate solution.

2. Purification of metals

Electrolytic refining is a process used to purify metals by removing impurities through electrolysis. A common example of this is the refining of copper.

3. Production of chemicals

Some chemicals are made using electrolysis, such as chlorine and sodium hydroxide, from the electrolysis of brine (a concentrated salt solution).

4. Extraction of metals

Metals such as aluminum are extracted from their ores using electrolysis. It is particularly effective for extracting metals that are more reactive and cannot be obtained through simple reduction with carbon.

An in-depth look at electrolytic cell components

  • Electrolyte: Generally, an electrolyte is a compound that dissociates into ions when dissolved in water or melted. It must have freely moving ions to conduct electricity. Common examples include H 2 SO 4 and NaCl.
  • Electrode: The electrodes connect the electrolyte to an external circuit. The material of the electrodes can affect the process, as they must be chemically inert enough to not dissolve during electrolysis.
  • Power supply: Electrical current is supplied to the electrolytic cell via a direct current (DC) power source, providing the external energy needed for the reaction.

Factors affecting electrolysis

An understanding of various factors is required to operate and optimize the electrolysis process:

1. Nature of electrolyte

The type of ions present affects the products of electrolysis. Different electrolytes produce different elements or compounds at the electrodes.

2. Concentration of ions

The concentration of ions can affect the rate of electrolysis and sometimes the products, particularly when there are multiple ion types competing for electron transfer.

3. Electrode material

Although ideally inert, some electrodes may participate in reactions, and affect the electrolysis products.

4. Applied voltage

The applied voltage or electrical potential affects which reactions will occur. Higher voltages can promote more challenging chemical reactions.

5. Temperature

Increasing the temperature generally increases the reaction rate because the ions move faster, potentially affecting the efficiency and outcome of the electrolysis.

Quantitative aspects of electrolysis

Faraday's laws of electrolysis

Michael Faraday established laws describing how quantities of substances are liberated during electrolysis. These laws form the basis for understanding the quantitative aspects:

Faraday's first law of electrolysis:

The mass of material deposited or released at an electrode is directly proportional to the amount of electricity passed through the electrolyte.

m = ZQ where m is the mass, Z is the electrochemical equivalent, and Q is the total electric charge.

Faraday's second law of electrolysis:

When the same amount of electricity is passed through different electrolytes, the mass of the substance liberated at the electrode is proportional to their equivalent weights.

Challenges and considerations in electrolysis

Despite being widely useful, electrolysis processes come with a variety of challenges and considerations:

Energy consumption

Electrolysis can be energy-intensive, often requiring cost and efficiency considerations, especially for industrial-scale applications.

Electrode reactions

Undesirable side reactions at the electrodes may result in the generation of impurities and affect production.

Material durability

Electrodes and cell containers must withstand corrosive environments to prevent corrosion and contamination.

Conclusion

Electrolysis is an integral part of modern chemistry, having diverse applications in industry and applied chemistry. Understanding its principles, factors affecting the process, and managing the challenges allows for efficient and effective use in a variety of chemical transformations. From simple laboratory applications to sophisticated industrial productions, electrolysis remains a cornerstone of chemical engineering and materials science.


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Electrolysis

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