NEET Notes: Electrochemistry

Introduction

Electrochemistry is the branch of chemistry that studies the relationship between electrical energy and chemical reactions. It plays a crucial role in various applications, including batteries, fuel cells, electrolysis, and corrosion prevention. Understanding electrochemical processes is essential for NEET aspirants, as it bridges concepts from both chemistry and physics.

Electrochemical Reactions

1. Definition of Electrochemical Reactions

Electrochemical reactions involve the interconversion of chemical and electrical energy. These reactions take place in electrochemical cells and can be spontaneous or non-spontaneous.

2. Types of Electrochemical Reactions

• Oxidation: Loss of electrons from a substance.

• Reduction: Gain of electrons by a substance.

• Redox Reactions: Chemical reactions where oxidation and reduction occur simultaneously.

Electrochemical Cells

1. Galvanic (Voltaic) Cells

A galvanic cell is a device that generates electrical energy from a spontaneous redox reaction. It consists of two half-cells, each containing an electrode and an electrolyte.

2. Components of a Galvanic Cell

• Anode: The electrode where oxidation occurs.

• Cathode: The electrode where reduction occurs.

• Salt Bridge: Maintains electrical neutrality by allowing ion flow between half-cells.

• Electrolyte Solution: Contains ions that participate in the reaction.

3. Example: Daniell Cell

The Daniell cell is a common example of a galvanic cell, using zinc and copper electrodes immersed in their respective salt solutions.

Electrode Potential

1. Definition of Electrode Potential

Electrode potential is the potential difference between an electrode and its electrolyte solution. It determines the tendency of an electrode to lose or gain electrons.

2. Standard Electrode Potential (E°)

The standard electrode potential is measured under standard conditions (1M concentration, 1 atm pressure, 25°C temperature).

3. Electrochemical Series

The electrochemical series ranks elements based on their standard electrode potentials. It helps predict the feasibility of redox reactions.

Nernst Equation

1. Importance of the Nernst Equation

The Nernst equation calculates the electrode potential at non-standard conditions. It helps in determining the cell potential in real-life applications.

2. Factors Affecting Electrode Potential

• Concentration of ions in solution.

• Temperature changes.

• Pressure (for gaseous reactions).

Electrolysis and Electrolytic Cells

1. Definition of Electrolysis

Electrolysis is the process of using electrical energy to drive a non-spontaneous chemical reaction. It occurs in electrolytic cells, which are different from galvanic cells.

2. Components of an Electrolytic Cell

• Anode: The positive electrode where oxidation occurs.

• Cathode: The negative electrode where reduction occurs.

• Electrolyte: The solution or molten substance that conducts electricity.

3. Applications of Electrolysis

• Electroplating: Coating a metal surface with another metal.

• Purification of Metals: Used in refining metals like copper and aluminum.

• Production of Chemicals: Electrolysis is used to produce chlorine, hydrogen, and sodium hydroxide.

Faraday’s Laws of Electrolysis

1. First Law of Electrolysis

The mass of a substance deposited or liberated during electrolysis is directly proportional to the quantity of electricity passed.

2. Second Law of Electrolysis

When the same amount of electricity passes through different electrolytes, the masses of substances deposited are proportional to their equivalent weights.

Batteries and Fuel Cells

1. Definition of Batteries

Batteries are electrochemical cells that store and provide electrical energy. They are widely used in everyday applications.

2. Types of Batteries

• Primary Batteries: Non-rechargeable, such as dry cells and alkaline batteries.

• Secondary Batteries: Rechargeable, such as lead-acid batteries and lithium-ion batteries.

3. Fuel Cells

Fuel cells generate electricity by continuously supplying reactants. They are efficient and environmentally friendly.

Corrosion and Its Prevention

1. Definition of Corrosion

Corrosion is the gradual deterioration of metals due to chemical reactions with the environment.

2. Causes of Corrosion

• Reaction with oxygen and moisture.

• Presence of acids or salts in the environment.

3. Prevention of Corrosion

• Galvanization: Coating iron with zinc.

• Painting and Coating: Prevents direct contact with air and moisture.

• Cathodic Protection: Using a sacrificial anode to prevent rusting.

Importance of Electrochemistry in NEET

1. Role in Biological Processes

Electrochemical reactions are crucial in nerve signal transmission and energy production in cells.

2. Industrial Applications

Electrochemistry is used in metal extraction, electroplating, and chemical production.

3. Environmental and Medical Applications

• Water purification through electrolysis.

• Medical diagnostics using electrochemical sensors.

Conclusion

Electrochemistry is a fundamental topic in chemistry with numerous real-life applications. From batteries and fuel cells to corrosion prevention and industrial electrolysis, understanding electrochemical concepts is essential for NEET aspirants. Mastery of electrochemical cells, electrode potential, and electrolysis is crucial for solving numerical and conceptual problems in exams.