Chemical Reaction and Equations

  

Chemical Equations and Reactions – A Detailed Guide for Class 10 CBSE

Introduction

Chemical reactions are the foundation of chemistry, enabling the transformation of substances. A chemical equation is a symbolic representation of a chemical reaction, showing the reactants and products.

1. Chemical Reactions

A chemical reaction is a process in which one or more substances (reactants) undergo a transformation to form new substances (products). The reaction is usually accompanied by changes such as:

  • Change in state (solid, liquid, gas formation)

  • Change in color (e.g., rusting of iron)

  • Evolution of gas (e.g., reaction of acids with metals)

  • Change in temperature (exothermic and endothermic reactions)

2. Chemical Equations

A chemical equation represents a chemical reaction using symbols and formulas of the reactants and products.

Balanced Chemical Equations

A balanced equation has equal numbers of atoms of each element on both sides, ensuring the Law of Conservation of Mass is followed.

Types of Chemical Equations

  1. Skeletal Equation – Unbalanced representation of a reaction.

  2. Balanced Equation – Follows the Law of Conservation of Mass.

3. Types of Chemical Reactions

(a) Combination Reaction

Two or more reactants combine to form a single product.

(b) Decomposition Reaction

A single compound breaks down into two or more simpler substances.
Types:

  1. Thermal decomposition – Requires heat.

  2. Electrolytic decomposition – Uses electricity.​

  3. Photolytic decomposition – Requires light.

(c) Displacement Reaction

A more reactive element replaces a less reactive element in a compound.

(d) Double Displacement Reaction

Exchange of ions between reactants to form new compounds.

(e) Redox Reactions

  • Oxidation – Gain of oxygen / loss of hydrogen.

  • Reduction – Loss of oxygen / gain of hydrogen.

4. Effects of Oxidation in Daily Life

(a) Corrosion

  • Metals react with air and moisture, leading to rusting.

  • Example: Iron reacts with oxygen and water to form iron oxide (rust).

(b) Rancidity

  • Oxidation of oils and fats leading to a foul smell.

  • Prevented by refrigeration, antioxidants, and airtight storage.

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