Redox Reactions

For JEE Exams:

Oxidation and Reduction

• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.

Types of Redox Reactions

• Combination: Two or more substances combine to form a new substance.
• Decomposition: A single substance breaks down into two or more new substances.
• Displacement: One element replaces another element in a compound.
• Disproportionation: A single substance undergoes both oxidation and reduction simultaneously.

Balancing Redox Reactions (Half-reaction method)

• Split the overall reaction into two half-reactions: oxidation half-reaction and reduction half-reaction.
• Balance each half-reaction separately.
• Multiply the oxidation half-reaction by a suitable factor to make the number of electrons lost equal to the number of electrons gained in the reduction half-reaction.
• Add the two half-reactions together to obtain the overall balanced redox reaction.

Redox Reactions in Acidic and Basic Solutions

• In acidic solutions, H+ ions are involved in the reactions.
• In basic solutions, OH- ions are involved in the reactions.

Redox Reactions and Electrochemical Cells

• Electrochemical cells convert chemical energy into electrical energy.
• Redox reactions occur at the anode (oxidation) and the cathode (reduction) of the electrochemical cell.
• The cell potential (Ecell) is the difference in potential between the anode and the cathode.

Nernst Equation and Cell Potential

• The Nernst equation relates the cell potential to the concentrations of reactants and products.
• The cell potential decreases with increasing temperature.
• The cell potential is positive if the reaction is spontaneous and negative if the reaction is non-spontaneous.

Determination of pH of solutions using redox reactions

• Redox reactions can be used to determine the pH of solutions by measuring the cell potential.
• The pH of a solution can be calculated using the following equation:

pH = (Ecell - E^0) / (0.0592 V/pH)

For CBSE Board Exams:

Oxidation and Reduction

• Oxidation: Loss of electrons or an increase in oxidation number.
• Reduction: Gain of electrons or a decrease in oxidation number.

Types of Redox Reactions

• Combination: Two substances combine to form a new substance.
• Decomposition: A single substance breaks down into two or more new substances.
• Displacement: One element replaces another element in a compound.

Balancing Redox Reactions (Simple cases)

• Balance the number of atoms of each element on both sides of the reaction.
• Balance the charge on both sides of the reaction.
• Balance the mass on both sides of the reaction.

Role of Redox Reactions in Everyday Life

• Redox reactions are involved in many everyday processes, such as:
  • Respiration
  • Combustion
  • Rusting of iron
  • Photosynthesis

Corrosion and its Prevention

• Corrosion is the process by which metals react with oxygen and water to form oxides.
• Corrosion can be prevented by:
  • Painting or coating the metal with a protective layer.
  • Applying a sacrificial anode.