17.7 Electrolysis
3 min read•june 25, 2024
is a fascinating process that uses electricity to drive chemical reactions. It's all about splitting compounds into their elements or depositing metals onto surfaces. This technique is crucial in many industries, from metal refining to producing important chemicals.
Understanding helps us grasp how we can harness electrical energy to make or break chemical bonds. It's a key part of , showing how we can control and manipulate chemical reactions using electricity. Pretty cool stuff!
Electrolysis
Steps and components of electrolysis
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- Electrolysis uses electrical energy from an external power source (battery or electrical outlet) to drive a non-spontaneous redox reaction
- components include an (ionic compound dissolved in water or molten state) and two electrodes ( and ) submerged in the electrolyte
- Cathode is the negative electrode where reduction occurs and gain electrons
- is the positive electrode where oxidation occurs and lose electrons
- Dissociation of the electrolyte into cations and anions when dissolved or molten
- Migration of ions with cations moving towards the cathode and anions moving towards the anode
- Examples of electrolysis include (depositing a thin metal layer onto an object), (purifying metals by separating them from impurities), and production of elements (extracting reactive metals like sodium from their compounds)
Electrolytic vs galvanic cells
- Electrolytic cells require an external power source to drive a non-spontaneous redox reaction, converting electrical energy into chemical energy
- Reduction occurs at the cathode and oxidation occurs at the anode
- Applications include , electrolytic refining, and production of elements
- () generate electrical energy from a spontaneous redox reaction, converting chemical energy into electrical energy
- Reduction occurs at the cathode (positive electrode) and oxidation occurs at the anode (negative electrode)
- Applications include batteries, fuel cells, and electrochemical sensors
- Key differences between electrolytic and galvanic cells:
- Energy source (external power vs self-generated)
- Reaction spontaneity (non-spontaneous vs spontaneous)
- Energy conversion (electrical to chemical vs chemical to electrical)
Faraday's laws in electrolysis calculations
- relate the amount of substance produced or consumed during electrolysis to the quantity of electrical charge passed through the cell
- First law states that the mass of a substance altered at an electrode is directly proportional to the quantity of electricity transferred at that electrode
- Mathematically expressed as , where is mass, is a constant, and is charge transferred
- Second law states that the masses of different substances altered by the same quantity of electricity are proportional to their (molar mass divided by the number of electrons transferred per formula unit)
- Calculate the mass of a substance produced during electrolysis using
- is mass, is charge passed (coulombs), is molar mass, is number of electrons transferred per formula unit, and is (96,485 C/mol)
- Calculate the volume of a gas produced during electrolysis using the ideal gas law
- is pressure, is volume, is number of moles (calculated using Faraday's laws), is gas constant, and is temperature
Electrochemistry fundamentals
- Electrochemistry is the study of chemical processes that cause electrons to move, including electrolysis and galvanic cells
- (redox reactions) involve the transfer of electrons between species
- describe the separate oxidation and reduction processes occurring at each electrode
- are substances that conduct electricity when dissolved in water or molten, due to the presence of ions
- of an electrolyte solution depends on the concentration and mobility of ions present
Key Terms to Review (23)
Anions: Anions are negatively charged ions that form when an atom or molecule gains one or more electrons. They are an essential component in the formation of ionic and molecular compounds, playing a crucial role in various chemical processes and phenomena.
Anode: The anode is the electrode where oxidation occurs in a galvanic cell. It is typically the negative terminal in such cells.
Anode: The anode is the electrode in an electrochemical cell where oxidation occurs, and electrons are released to flow through an external circuit. It is the negatively charged electrode that attracts positively charged ions and initiates the flow of electrons in a redox reaction.
Cathode: A cathode is an electrode where reduction occurs during an electrochemical reaction. It plays a crucial role in various processes such as galvanic cells, where it attracts cations from the electrolyte, facilitating the flow of electric current. Understanding the function of the cathode is essential for grasping concepts like electrode potentials and energy transformations in electrochemical cells.
Cations: Cations are positively charged ions that form when an atom loses one or more of its valence electrons. They are a fundamental concept in understanding ionic and molecular compounds, ionic bonding, electrolysis, and periodicity.
Electrical conductivity: Electrical conductivity is the ability of a material to conduct electric current, which is influenced by the presence and mobility of charged particles such as ions or electrons. Materials with high electrical conductivity allow electricity to flow easily, while those with low conductivity resist it. This concept is essential in understanding how different types of bonding and chemical processes, like electrolysis, affect the flow of electricity.
Electrochemistry: Electrochemistry is the study of the relationship between electrical energy and chemical energy, and the interconversion between the two. It involves the study of chemical reactions that produce electricity and the use of electrical energy to drive chemical reactions.
Electrolysis: Electrolysis is a chemical process in which electrical energy is used to drive a non-spontaneous chemical reaction. It involves passing an electric current through an electrolyte, causing ions to move and resulting in the deposition of substances at the electrodes.
Electrolysis: Electrolysis is the process of using electric current to drive a non-spontaneous chemical reaction. It involves the decomposition of chemical compounds by passing an electric current through them, resulting in the separation of their constituent elements. This process is fundamental to various applications, including the production of metals, the treatment of water, and the recharging of batteries.
Electrolyte: An electrolyte is a substance that, when dissolved in a solvent such as water, dissociates into charged particles called ions. These ions are capable of conducting electricity and are essential for various chemical and physiological processes in the body and in electrochemical devices.
Electrolytes: Electrolytes are substances that dissociate into ions when dissolved in water, allowing the solution to conduct electricity. Common examples include salts, acids, and bases.
Electrolytic Cell: An electrolytic cell is an electrochemical cell that uses an external electrical current to drive a non-spontaneous redox reaction. It is a device that converts electrical energy into chemical energy through the process of electrolysis.
Electrolytic refining: Electrolytic refining is a process used to purify metals by utilizing electrolysis, where an impure metal serves as the anode and a pure metal layer is deposited at the cathode. This technique is especially significant for extracting high-purity transition metals, as it allows for the separation of valuable metals from impurities through controlled electrical energy. By converting the metal ions back into solid form at the cathode, electrolytic refining produces metals that meet stringent purity standards needed for various industrial applications.
Electroplating: Electroplating is a process that uses electrical current to deposit a thin layer of metal onto the surface of another material. It is commonly used for improving corrosion resistance, enhancing appearance, and reducing friction.
Electroplating: Electroplating is an electrochemical process used to deposit a thin layer of one metal onto the surface of another metal, typically for the purposes of decoration, corrosion protection, or to impart specific properties. It involves the use of an electric current to reduce dissolved metal cations so that they form a coherent metal coating on an electrode.
Equivalent Weights: Equivalent weight is a concept in chemistry that describes the mass of a substance that will react with or displace a fixed amount of another substance, such as one gram of hydrogen or one equivalent of a given reagent. It is an important consideration in the context of electrochemical processes like electrolysis.
Faraday's Constant: Faraday's constant is a fundamental physical constant that represents the amount of electric charge carried by one mole of electrons. It is a crucial parameter in electrochemical processes and is essential for understanding the relationship between electrical and chemical quantities.
Faraday's Laws: Faraday's laws are two fundamental principles that describe the relationship between electricity and chemical reactions, particularly in the process of electrolysis. These laws were formulated by the English scientist Michael Faraday in the 1830s and are essential for understanding the quantitative aspects of electrochemical processes.
Galvanic Cells: A galvanic cell, also known as a voltaic cell, is an electrochemical cell that generates an electric current through a spontaneous redox (reduction-oxidation) reaction. It is the basic unit of a battery, where chemical energy is converted into electrical energy.
Half-Reactions: Half-reactions are the individual reduction and oxidation processes that occur during a redox (reduction-oxidation) reaction. They represent the separate steps in which electrons are either gained or lost by the reactants, allowing for the overall balanced equation to be determined.
Oxidation-Reduction Reactions: Oxidation-reduction reactions, also known as redox reactions, are chemical reactions in which the oxidation state of atoms changes. This involves the transfer of electrons between chemical species, with one substance becoming oxidized (losing electrons) and another becoming reduced (gaining electrons).
Oxyanions: Oxyanions are polyatomic ions that contain one or more oxygen atoms bonded to another element, typically a non-metal. They often carry a negative charge due to the presence of extra electrons.
Voltaic Cells: A voltaic cell, also known as a galvanic cell, is an electrochemical cell that generates an electric current from a spontaneous redox (reduction-oxidation) reaction. It consists of two different metallic electrodes immersed in an electrolyte solution, which allows the flow of ions and the generation of a potential difference between the electrodes.