“Master Redox Reactions – Class 11 CBSE Chemistry Made Simple”

Introduction to Redox Reactions

Redox reactions, short for reduction-oxidation reactions, are chemical processes in which oxidation and reduction occur simultaneously. These reactions are fundamental to many chemical processes and are essential for understanding concepts in physical chemistry.

Key Definitions

1. Oxidation: Loss of electrons or increase in oxidation state of an atom or ion.
2. Reduction: Gain of electrons or decrease in oxidation state of an atom or ion.
3. Oxidizing Agent: Substance that gains electrons (is reduced).
4. Reducing Agent: Substance that loses electrons (is oxidized).

Examples:

• Oxidation Reaction:
• Reduction Reaction:
• Redox Reaction:

Types of Redox Reactions

1. Combination Reactions: Two or more substances combine to form a single product. Example:
2. Decomposition Reactions: A single compound breaks down into two or more products. Example:
3. Displacement Reactions: One element displaces another in a compound. Example:
4. Disproportionation Reactions: A single substance undergoes both oxidation and reduction. Example:

Oxidation Numbers

The oxidation number (or state) of an element in a compound indicates the number of electrons lost, gained, or shared by that element.

Rules for Assigning Oxidation Numbers:

1. The oxidation number of an element in its elemental form is zero (e.g., O, N).
2. The oxidation number of a monoatomic ion is equal to its charge (e.g., Na = +1).
3. In compounds, hydrogen is usually +1, and oxygen is usually -2, except in peroxides (-1 for oxygen).
4. The sum of oxidation numbers in a neutral compound is zero, and in a polyatomic ion, it equals the ion’s charge.

Example:

For :

• H = +1 (2 atoms = +2)
• O = -2 (4 atoms = -8)
• S must be +6 to balance the total to 0.

Balancing Redox Reactions

Redox reactions can be balanced using two methods:

1. Oxidation Number Method:
   • Assign oxidation numbers to all elements.
   • Identify changes in oxidation numbers.
   • Balance changes in oxidation numbers using coefficients.
   • Balance other atoms and charges.
2. Ion-Electron Method (Half-Reaction Method):
   • Split the reaction into oxidation and reduction half-reactions.
   • Balance atoms and charges in each half-reaction.
   • Combine the half-reactions, ensuring electrons are canceled out.

Example:

Balance :

1. Oxidation half-reaction:
2. Reduction half-reaction:
3. Combine and balance electrons: .

Applications of Redox Reactions

1. Industrial Processes: Extraction of metals, electroplating, and manufacturing of chemicals like chlorine and sodium hydroxide.
2. Biological Systems: Cellular respiration and photosynthesis involve redox processes.
3. Electrochemical Cells: Batteries and galvanic cells work on redox principles.

Summary

Redox reactions are integral to chemistry and are characterized by simultaneous oxidation and reduction. Understanding oxidation numbers, balancing techniques, and types of reactions is crucial for mastering this topic in Class 11 CBSE syllabus

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