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Chapter 3 – Electrochemistry

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Electrochemistry is everywhere around you, in the batteries of your laptop or mobile to the clock on your wall. It is one of the most important disciplines of chemistry. It is a study of electricity and its reaction to chemical changes. The electricity is generated by the movement of electrons from one element to another under electrochemistry. This reaction is known as redox or oxidation-reduction reaction. These reactions can be classified, into two:-

  • Chemical change production through electrical energy. (the phenomenon of electrolysis)
  • Chemical energy conversion into electrical energy. (By spontaneous redox reactions, generation of electricity)

Electrochemistry basically deals with overall reactions when simultaneously connected multiple redox reactions occur. These notes will help you understand the core concept of Electrochemistry and exam revisions as well.

A chemical process that can take place on its own and Gibbs free energy of a system decreases. In electrochemistry, the conversion of chemical energy into electrical energy is due to a redox reaction. Where a non-spontaneous chemical reaction occurs due to supplying energy, the reverse process is also possible. The interconversion that takes place in equipment is called an electrochemical cell.

Types of Electrochemical Cell

  • Galvanic Cells: The chemical energy is converted into electrical energy through Galvanic Cells. Redox reaction helps to obtain electricity. In two separate compartments oxidation and reduction take place. Both Electrolyte solution and metallic conductor which acts as an electrode, present in each compartment. 

Example:- For a redox reaction to take place, the Daniell cell in a galvanic cell consists of zinc, and copper is used. 

Zn(s) + Cu+2(aq) → Zn+2 + Cu(s)

At anode (oxidation half)

Zn(s) →Zn+2 + 2e–

At the cathode (reduction half)

Cu+2(aq) + 2e– → Cu(s)

  • Electrolytic Cells: The process through which electrical energy is converted to chemical energy is called Electrolytic Cells. The electrolytic solutions which contain cations and anions the electrons are dipped into it. The ions move towards electrodes of opposite polarity after supplying current. As a result, simultaneous reduction and oxidation take place.

The cell’s electrode potential and the emf depends upon the nature of the electrode, temperature, and the activities of ions in solution.

For the general electrochemical reaction of the types:

aA + bB → cC +dD

Ecell = Eocell – RT/ nF ln [C]c [D]d / [A]a [B]b

Ecell = Eocell – 2.0303 RT / nF log [C]c [D]d / [A]a [B]b

Ecell = Eocell – 0.0591 / n log [C]c [D]d / [A]a [B]b at 298K

The concept of electrolysis was given by Faraday. The amount of substance deposited is proportional to the quantity when an electric current is passed, through an electrolyte.

Batteries

 

1. brass cap,

2. plastic seal,

3. expansion space,

4. porous cardboard,

5. zinc can,

6. carbon rod,

7. chemical mixture

An arrangement of electrochemical cells which is used as energy is called a battery. The oxidation-reduction is the basis of an electrochemical cell. The following are the requirements of a useful battery:-

  • It should be easily transported and should be light and compact.
  • During use, the voltage of the battery should not vary. 
  • Whether it is in use or not, it should have a long life.

They are of two types:

  • Primary Cells: The electrode reactions cannot be reversed in these cells by an external energy source. Examples – dry cell and mercury cell.
  • Secondary Cells:  The electrode reactions can be reversed in these cells by an external energy source. Examples – lead storage battery and nickel-cadmium storage cell.

When an electrochemical cell generates electrical energy from fuel with the help of an electrochemical reaction, then it is called a fuel cell. Electrochemical cells are somewhat similar to a fuel cell.

Working of a Fuel Cell

Hydrogen and oxygen reaction is used to generate electricity via a fuel cell. The hydrogen and oxygen are passed, through a concentrated solution of sodium hydroxide. The reaction can be written as:-

Cathode Reaction: O2 + 2H2O + 4e– → 4OH–

Anode Reaction: 2H2 + 4OH– → 4H2O + 4e–

Net Cell Reaction: 2H2 + O2 → 2H2O

Examples of Fuel Cells

  • The Polymer Electrolyte Membrane Fuel Cell
    In this cell temperature range from 50oC to 100o and, it is also called proton exchange membrane fuel cells.
  • Phosphoric Acid Fuel Cell
    It is used to channel the H+ with the help of phosphoric acid. The Working temperature is between 150oC – 200oC.

When a pure metal is transformed into some undesirable substance as it comes in contact with water and air. However, this reaction causes damage to metal. Some of the examples are copper corrosion, silver tarnishing, and rusting. 

Types of Corrosion

  • Crevice Corrosion: It occurs when there is a difference in ionic concentration between two local areas of metal. 
  • Stress Corrosion Cracking: Cracking of a metal due to corrosion environment. It occurs due to high temperatures. 
  • Uniform Corrosion: It happened due to the atmosphere and a very common type of corrosion. It is easily discernible.
  • Pitting Corrosion: It is difficult to detect and highly unpredictable.

The Electrolytic solution’s ability to allow the passage of electric current through them is called electrolytic conductance. The ion that is present in the solution rendered the ability which occurred due to the dissociation of the electrolyte. 

Factors affecting Electrolytic Conductance

  • The conductivity of electrolytes is due to ions present in them. 
  • The nature of electrolytes is significantly affected by electrolytic conduction. 
  • The degree to which an electrolyte gets dissolved in the solution is affected by temperature.

Electrochemistry plays a vital role in technological applications. To understand electrochemistry first, try to understand the core concept behind it with an explanatory video on the MSVgo app. The MSVgo philosophy is to enable a core understanding of any concept. The video library of the MSVgo app explains concepts with examples or explanatory visualizations or animations.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
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  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
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  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
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  • Metallurgy
  • Metals And Non-Metals
  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
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  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
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  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
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  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
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  • How Do Organisms Reproduce?
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  • Molecular Basis of Inheritance
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  • Photosynthesis
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  • Plant Growth and Development
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  • Principles of Inheritance and Variation
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  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
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  • The Endocrine System
  • The Fundamental Unit Of Life
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  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
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  • Geometry – Area
  • Geometry – Circles
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  • Geometry – Introduction to Euclid’s Geometry
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  • Linear Programming
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  • Mensuration – Areas
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  • Number Systems
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  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
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  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
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  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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