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Introduction to Electrochemistry: Powering the Future
Dive into the world of electrochemistry and uncover the secrets of redox reactions. Learn how electron transfer drives modern technology, from batteries to fuel cells, and explore its vast potential in science and industry.

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Now Playing:Introduction to electrochemistry – Example 0a
Intros
  1. What is electrochemistry?
  2. What is electrochemistry?
    The electrochemical cell
  3. What is electrochemistry?
    Redox reactions
Examples
  1. Identify whether reduction or oxidation is taking place in the half-equations.
    State whether the half-equations below show reduction or oxidation, giving a reason for your answer.
    1. Au  \, →  \, Au+ + e-

    2. Na  \, →  \, Na+ + e-

    3. Cl2 + 2e-  \, →  \, 2Cl-

Introduction to electrochemistry
Jump to:NotesConceptFAQsPrerequisites
Notes

In this lesson, we will learn:

  • The definition of electrochemical cell, reduction and oxidation.
  • How to write half equations showing oxidation and reduction.
  • How to identify oxidizing and reducing agents in reactions.
  • The activity series as a predictor of relative oxidative strength.

Notes:

  • Electrochemistry is similar to acid and base chemistry. Think about some of the key points we saw in in the Acid-Base theory and Solubility equilibria chapters:
    • Acids and bases are ionic substances that make ionic solutions when dissolved.
    • Acids and bases react with each other and with metals to produce salts, which are also ionic substances that make ionic solutions when dissolved.
    • Ionic solutions conduct electricity.
    • Reactions between some acids and bases or salts can release lot of energy.

      The reactions that release energy can be set up in chemical ‘circuits’ called electrochemical cells. An electrochemical cell is a system that converts chemical potential energy into electrical energy. The electrical energy (electricity!) is produced by the movement of electrons from one of the reactants to another. See example diagram below.

      Because electrons are negatively charged, reactions in electrochemical cells will always result in at least two of the atoms or ions in the reaction changing their individual charge. One is the atom losing the electrons and one is the atom gaining these electrons.

  • Any reaction where an atom or ion changes its individual charge is called a redox reaction. The word redox comes from reduction and oxidation, the two opposite effects happening in a redox reaction.
    • Reduction is when any atom or compound gains electrons, hydrogen, or loses oxygen.
    • Oxidation is when any atom or compound loses electrons, hydrogen, or gains oxygen.
    Reduction and oxidation are complementary – one cannot happen without the other. This means that if there is a chemical being reduced in a reaction, there will be a chemical getting oxidized (that’s why the overall reaction is called redox!).

    There is a trick to remember what oxidation and reduction do in chemical reactions – OIL-RIG:
    • Oxidation Is Loss (OIL) of electrons or hydrogen.
    • Reduction Is Gain (RIG) of electrons or hydrogen.

  • Any redox reaction can be split up to show reduction and oxidation separately in a half-equation. To do this, you need to use electrons to show the atom either gaining or losing electrons. We use the symbol e- to do this.
    For example, the two-electron oxidation of copper can be written in a half-equation:

    Cu  \, →  \, Cu2+ +  \, 2e-

    The reduction of chlorine can be written in a half-equation:

    Cl2 + 2e-  \, →  \, 2Cl-

    In half-equations, electrons in the reactants show reduction, and electrons in the products show oxidation.

    The e- symbol for electrons is ONLY used in half-equations; do not use it in full equations. In full equations showing the ‘real’ process, those electrons are contained in the other chemical that is being reacted!

  • Chemicals that reduce other chemicals are called reducing agents, while chemicals that oxidize other chemicals are called oxidizing agents.
    An agent or agency is someone/something that does things – a reducing agent does reduction to other chemicals, so the reducing agent itself is oxidized! Do not get them confused!
    We learned in lessons like Electron configuration 2 and Forming ions that some atoms tend to gain or lose electrons to obtain a full outer shell of electrons. If you know this already, then you already have a good idea of what elements are reducing and oxidizing agents!
    • Most reducing agents are metals because metals, as we know, normally lose electrons in a reaction, becoming positive ions while the other species in the reaction gains those electrons.
    • Most oxidizing agents are electronegative non-metals that, as we know, tend to gain electrons in reactions by ‘removing them’ from other elements. Fluorine is an excellent oxidizing agent, as is oxygen (that’s why it’s called oxidation!) and chlorine – these are the most electronegative elements in the table.

  • The activity series is a basic list that shows the relative tendencies of metal species to be oxidised – that is, to go from the elemental metal to metal ion plus electron(s). This has a correlation with electronegativity, as group 1 and 2 metals are amongst the highest in the series, like calcium, potassium and lithium. Near the bottom are the heavier transition metals like mercury, platinum and gold.
    The activity series is based on standard electrode potential (AKA standard reduction potential) which we will use in calculations in the later lesson Calculating cell potential (Voltaic cells).
Concept

Introduction to Electrochemistry

Electrochemistry is a fascinating branch of chemistry that explores the relationship between electrical and chemical processes. At its core are redox reactions, where electrons are transferred between species, leading to changes in oxidation states. These reactions form the basis of electrochemical cells, devices that convert chemical energy into electrical energy or vice versa. Electrochemistry has numerous practical applications, from batteries and fuel cells to corrosion prevention and electroplating. The introduction video serves as a crucial starting point for understanding these fundamental concepts. It provides a visual representation of electron flow, explains the structure of electrochemical cells, and demonstrates how redox reactions drive the generation of electricity. By grasping these basic principles, students can better appreciate the role of electrochemistry in modern technology and its potential for solving energy-related challenges. This foundation is essential for delving deeper into more complex electrochemical phenomena and their wide-ranging applications in science and industry.

FAQs

  1. What is the difference between oxidation and reduction?

    Oxidation is the loss of electrons by a species, resulting in an increase in its oxidation state. Reduction is the gain of electrons by a species, resulting in a decrease in its oxidation state. These processes always occur together in redox reactions, with one species being oxidized while another is reduced.

  2. How does an electrochemical cell work?

    An electrochemical cell converts chemical energy into electrical energy through redox reactions. It consists of two half-cells connected by a salt bridge. At the anode, oxidation occurs, releasing electrons that flow through an external circuit to the cathode, where reduction takes place. The salt bridge maintains electrical neutrality by allowing ion flow between the half-cells.

  3. What is the significance of the activity series in chemistry?

    The activity series ranks metals based on their reactivity, with more reactive metals at the top. It helps predict the outcomes of reactions involving metals, such as displacement reactions. Metals higher in the series can replace those lower in compounds. This information is crucial in fields like metallurgy and corrosion prevention.

  4. How are standard reduction potentials used in electrochemistry?

    Standard reduction potentials provide a quantitative measure of a species' tendency to be reduced. They are used to calculate cell potentials, predict the spontaneity of redox reactions, and determine the direction of electron flow in electrochemical cells. The more positive the reduction potential, the greater the tendency for the species to be reduced.

  5. What are some practical applications of electrochemistry?

    Electrochemistry has numerous practical applications, including:

    • Batteries and fuel cells for energy storage and conversion
    • Electroplating for coating metals
    • Corrosion prevention in metal structures
    • Water treatment and purification
    • Sensors for chemical and biological detection
    These applications rely on the principles of redox reactions and electron transfer to achieve their specific functions.

Prerequisites

Before diving into the fascinating world of electrochemistry, it's crucial to have a solid foundation in certain fundamental chemistry concepts. Two key prerequisite topics that play a significant role in understanding electrochemistry are the history and development of the periodic table and balancing chemical equations.

The periodic table is a cornerstone of chemistry, and its understanding is vital for electrochemistry. The arrangement of elements in the periodic table provides crucial information about their electronic structure and chemical properties. In electrochemistry, we often deal with redox reactions involving various elements, and knowing their position in the periodic table helps predict their behavior in electrochemical processes. The periodic table trends such as electronegativity, atomic radius, and ionization energy are particularly relevant when studying electron transfer reactions in electrochemistry.

Equally important is the skill of balancing chemical equations. Electrochemistry involves numerous reactions, often complex ones, that need to be properly balanced. When dealing with electrochemical cells or electrolysis processes, you'll frequently encounter half-reactions that must be balanced correctly. The ability to balance equations ensures that you can accurately represent the transfer of electrons in redox reactions, which is at the heart of electrochemistry. Moreover, balancing chemical equations is essential for stoichiometric calculations in electrochemical systems.

Understanding these prerequisite topics provides a strong foundation for grasping more advanced electrochemical concepts. For instance, knowledge of the periodic table helps in predicting the standard reduction potentials of elements, while proficiency in balancing equations is crucial when working with the Nernst equation or calculating cell potentials. As you delve deeper into electrochemistry, you'll find that these fundamental skills are constantly applied and built upon.

By mastering the periodic table and equation balancing, you'll be better equipped to understand the principles of electrochemistry, such as electrode processes, electrochemical cells, and the applications of electrochemistry in various fields like battery technology, corrosion prevention, and electroplating. These prerequisite topics serve as the building blocks for more complex electrochemical theories and applications, making them indispensable for anyone looking to excel in this field.

In conclusion, a solid grasp of the periodic table and the ability to balance chemical equations are crucial stepping stones on your journey to mastering electrochemistry. These foundational concepts will continually support your learning and help you navigate the intricacies of electrochemical phenomena with greater ease and understanding.