JEE Chemistry Notes: Electrochemistry

Introduction to Electrochemistry

Electrochemistry deals with the study of chemical reactions that involve the transfer of electrons, commonly observed in processes like oxidation-reduction reactions. These reactions play a crucial role in several industrial processes, including electroplating, corrosion, and batteries. Understanding electrochemistry is essential for students preparing for JEE, as it combines both chemical and electrical principles.

Types of Electrochemical Cells

• Galvanic Cells
  A Galvanic cell is a device that converts chemical energy into electrical energy through spontaneous redox reactions. The flow of electrons from the anode to the cathode through an external circuit generates electricity. An example of a galvanic cell is the Daniell cell.

• Electrolytic Cells
  Electrolytic cells are devices that use electrical energy to drive non-spontaneous chemical reactions. The electrical energy supplied from an external power source causes oxidation at the anode and reduction at the cathode.

Electrode Potential

• Standard Electrode Potential (E°)
  The standard electrode potential is a measure of the individual potential of a reversible electrode at standard conditions (298K, 1 M concentration, 1 atm pressure). It helps in predicting the direction of electron flow in electrochemical cells.

• Nernst Equation
  The Nernst equation relates the electrode potential to the concentration of ions in the solution. It is useful for calculating the potential of an electrode when the conditions deviate from standard conditions.

Cell Potential and EMF

• Electromotive Force (EMF)
  The EMF of a cell is the potential difference between the anode and cathode when no current is flowing. It is a measure of the driving force of the electrochemical reaction.

• Relationship between Cell Potential and Gibbs Free Energy
  The cell potential is related to the Gibbs free energy change (ΔG) of the reaction through the equation:
  ΔG = −nFE_cell​
  Where nn is the number of moles of electrons, FF is the Faraday constant, and EcellEcell​ is the cell potential.

Electrolysis and Applications

• Faraday’s Laws of Electrolysis
  Faraday’s laws describe the relationship between the quantity of electric charge passed through an electrolyte and the amount of substance deposited or dissolved at the electrodes. The first law states that the amount of substance deposited is proportional to the quantity of charge, and the second law relates the amount of substance deposited to the equivalent weight of the substance.

• Applications of Electrolysis
  Electrolysis is used in various industrial processes, including electroplating, extraction of metals, and manufacturing of chemicals like chlorine and sodium hydroxide.

Corrosion

Corrosion is a process in which metals, especially iron, react with oxygen and moisture to form oxides, leading to degradation. The most common example is the rusting of iron. Electrochemical cells play a role in this process, with metal oxidation occurring at the anode and oxygen reduction at the cathode.

Jee Specific Practice Problems

• Understanding how to calculate the EMF of a cell.

• Applying the Nernst equation to determine the cell potential under non-standard conditions.

• Predicting the outcome of electrolysis reactions and calculating the amount of substance deposited using Faraday’s laws.

By mastering these fundamental concepts in Electrochemistry, students can confidently tackle related problems in JEE Chemistry and apply theoretical knowledge to real-world applications.