17.1 Review of Redox Chemistry
2 min read•june 25, 2024
reactions are all about electron swapping between chemicals. They're the basis for batteries, rust, and even how our bodies break down food. Understanding redox helps explain countless everyday processes and technologies.
Balancing redox equations can seem tricky, but it's just a step-by-step process. By breaking reactions into half-reactions and following a specific order, you can tackle even complex redox problems. This skill is crucial for predicting and controlling chemical reactions.
Fundamentals of Redox Chemistry
Fundamentals of redox chemistry
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- Redox reactions involve transfer of electrons between chemical species ()
- is loss of electrons by a species
- is gain of electrons by a species
- and reduction occur simultaneously in a redox reaction
- is reduced as it accepts electrons
- is oxidized as it donates electrons
- studies interconversion of electrical and chemical energy through redox reactions
- () generate electrical energy from spontaneous redox reactions (batteries)
- Electrolytic cells use electrical energy to drive non-spontaneous redox reactions (electroplating)
Oxidizing vs reducing agents
- Oxidizing agent accepts electrons and is reduced in the reaction
- Causes oxidation of another species by taking its electrons
- Examples: hydrogen peroxide (), permanganate ion (), chlorine gas ()
- Reducing agent donates electrons and is oxidized in the reaction
- Causes reduction of another species by giving it electrons
- Examples: sodium metal (), hydrogen gas (), iron metal ()
- Changes in oxidation numbers help identify oxidizing and reducing agents
- Increase in indicates oxidation occurred (reducing agent)
- Decrease in oxidation number indicates reduction occurred (oxidizing agent)
Electrochemical cells
- Consist of two half-cells connected by a salt bridge
- Each half-cell contains an electrode ( or ) immersed in an solution
- is the site of oxidation, where electrons are lost
- Cathode is the site of reduction, where electrons are gained
- Salt bridge allows ion flow to maintain electrical neutrality
- measures the tendency of a species to be reduced
Balancing Redox Equations
Balancing redox equations
- Separate overall reaction into two half-reactions
- Oxidation shows species losing electrons
- Reduction shows species gaining electrons
- Balance each half-reaction in this order:
- Balance all atoms except H and O
- Balance O atoms by adding molecules
- Balance H atoms by adding ions
- Balance charge by adding electrons ()
- Multiply half-reactions by factors to equalize electrons transferred
- Add balanced half-reactions and cancel out common terms
- Check that final equation is balanced for both atoms and charge
Key Terms to Review (33)
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.
Chemical reduction: Chemical reduction is a process in which an element or compound gains electrons, resulting in a decrease in its oxidation state. It often occurs alongside oxidation in redox reactions.
Cl2: Cl2 is the chemical formula for chlorine gas, a highly reactive and poisonous element that is part of the halogen group on the periodic table. Cl2 plays a significant role in various chemical processes and reactions, particularly in the context of redox chemistry, the occurrence and properties of phosphorus, and the occurrence, preparation, and properties of halogens.
E-: The symbol 'e-' represents an electron, the negatively charged subatomic particle that is a fundamental component of atoms and plays a crucial role in redox (reduction-oxidation) chemistry.
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.
Electrodes: Electrodes are conductors used to establish an electrical connection between a metallic part of a circuit and an electrified medium, such as an electrolyte solution or a plasma. They are essential components in electrochemical processes and devices, facilitating the transfer of electrons and enabling the flow of electric current.
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.
Electron Transfer: Electron transfer is the fundamental process in which electrons move from one atom or molecule to another, resulting in the formation of ionic bonds or redox reactions. This term is central to understanding both ionic bonding and redox chemistry.
Fe: Fe is the chemical symbol for the element iron, which is a transition metal that is essential for various biological processes in the human body. It plays a crucial role in the structure and function of many proteins and enzymes, particularly those involved in oxygen transport, energy production, and cellular respiration.
Galvanic Cell: 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 a device that converts the chemical energy of a spontaneous redox reaction into electrical energy.
Galvanic cells: Galvanic cells, also known as voltaic cells, are electrochemical cells that convert chemical energy into electrical energy through spontaneous redox reactions. They consist of two half-cells connected by a salt bridge and an external circuit.
H2: H2 is the chemical formula for the diatomic molecule of hydrogen, which is the simplest and most abundant element in the universe. This term is crucial in understanding the phases and classification of matter, writing and balancing chemical equations, as well as the principles of redox chemistry.
H2O2: Hydrogen peroxide (H2O2) is a chemical compound consisting of two hydrogen atoms and two oxygen atoms. It is a colorless liquid with a slightly pungent odor and is widely used in various applications, including disinfection, oxidation, and as a bleaching agent.
Half-reaction: A half-reaction is either the oxidation or reduction component of a redox reaction. It shows the loss or gain of electrons by a species.
Half-Reaction: A half-reaction is the oxidation or reduction of a single element or compound that occurs during a redox (reduction-oxidation) reaction. It represents the individual processes of losing or gaining electrons that take place on each side of a balanced chemical equation.
MnO4-: MnO4- is the chemical formula for the permanganate ion, a powerful oxidizing agent commonly used in various chemical reactions and processes. It is a key term in the context of reviewing redox chemistry.
Na: Na is the chemical symbol for the element sodium, which is a soft, silvery-white alkali metal that is highly reactive and essential for various physiological processes in the human body.
Oxidation: Oxidation is a chemical reaction where an atom, ion, or molecule loses electrons. It often involves gaining oxygen or losing hydrogen.
Oxidation: Oxidation is a fundamental chemical process in which an element or compound loses electrons, resulting in an increase in its oxidation state. This term is central to understanding redox (reduction-oxidation) reactions, the functioning of electrochemical cells, corrosion, and the properties and behavior of oxygen, sulfur, and various organic compounds.
Oxidation Number: The oxidation number is a numerical value assigned to an element in a chemical compound that represents the degree of oxidation of that element. It is a crucial concept in understanding redox (reduction-oxidation) reactions and the behavior of elements in chemical systems.
Oxidizing Agent: An oxidizing agent, also known as an oxidant, is a substance that has the ability to oxidize other substances by accepting electrons during a chemical reaction. Oxidizing agents are central to the understanding of redox chemistry and the functioning of electrochemical cells.
Oxidizing agent (oxidant): An oxidizing agent, or oxidant, is a substance that gains electrons in a chemical reaction and, in the process, causes another substance to be oxidized. It is reduced while the other substance is oxidized.
Redox: Redox, short for reduction-oxidation, is a fundamental chemical process that involves the transfer of electrons between chemical species. It is a crucial concept in chemistry that describes the exchange of electrons that occurs during chemical reactions, leading to the formation of new substances.
Reducing Agent: A reducing agent, also known as a reductant, is a substance that has the ability to reduce other substances by donating electrons in a chemical reaction. It is a key concept in the understanding of redox (reduction-oxidation) chemistry and the functioning of electrochemical cells.
Reducing agent (reductant): A reducing agent (reductant) is a substance that donates electrons to another substance in a chemical reaction, thereby reducing the oxidation state of the latter. It itself gets oxidized in the process.
Reduction: Reduction is a chemical process in which a substance gains electrons, resulting in a decrease in its oxidation state. It is a key concept in redox (reduction-oxidation) reactions, where substances are either reduced or oxidized to facilitate the transfer of electrons.
Standard Reduction Potential: The standard reduction potential, also known as the standard electrode potential, is a measure of the tendency of a chemical species to acquire electrons and be reduced. It is a fundamental concept in electrochemistry that helps determine the spontaneity and direction of redox reactions.
Voltaic Cell: A voltaic cell, also known as a galvanic cell, is an electrochemical cell that generates an electric current from a spontaneous redox reaction. It consists of two different metallic electrodes immersed in an electrolyte solution, where one electrode undergoes oxidation (the anode) and the other undergoes reduction (the cathode), creating a potential difference that drives the flow of electrons and generates an electric current.
Voltaic cells: Voltaic cells, also known as galvanic cells, are electrochemical cells that convert chemical energy into electrical energy through spontaneous redox reactions. They consist of two different metals connected by a salt bridge or porous membrane.