Chemical Reactions and Equations

Introduction to Chemical Reactions and Equations

Chemical reactions involve the transformation of one or more substances into new substances. A chemical equation is a representation of a chemical reaction using symbols and formulas.

Key Terms

• Reactant: A substance that is involved in a chemical reaction. (प्रतिक्रिया करने वाला पदार्थ)
• Product: A substance that is formed as a result of a chemical reaction. (उत्पाद)
• Catalyst: A substance that speeds up a chemical reaction without being consumed. (उत्प्रेरक)

Types of Chemical Reactions

• Combination Reaction: A reaction in which two or more substances combine to form a single product. (संयोजन अभिक्रिया)
• Decomposition Reaction: A reaction in which a single substance breaks down into two or more products. (विघटन अभिक्रिया)
• Displacement Reaction: A reaction in which one substance displaces another substance from a compound. (विस्थापन अभिक्रिया)
• Double Displacement Reaction: A reaction in which two substances exchange partners. (दोहरा विस्थापन अभिक्रिया)

Balancing Chemical Equations

To balance a chemical equation, the number of atoms of each element must be equal on both the reactant and product sides.

Laws of Chemical Reactions

• Law of Conservation of Mass: Matter cannot be created or destroyed in a chemical reaction. (द्रव्यमान संरक्षण का नियम)
• Law of Definite Proportions: A chemical compound always contains its component elements in fixed proportions by mass. (निश्चित अनुपात का नियम)

Key Formulas

• Combination Reaction: A + B → AB
• Decomposition Reaction: AB → A + B
• Displacement Reaction: A + BC → AC + B
• Double Displacement Reaction: AB + CD → AD + CB
• Mole Ratio: Moles of reactant 1 / Moles of reactant 2 = Coefficient of reactant 1 / Coefficient of reactant 2

Stoichiometry

• Mole: A unit of measurement that represents 6.022 x 10^23 particles (atoms or molecules).
• Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol).
• Empirical Formula: The simplest whole-number ratio of atoms of each element in a compound.
• Molecular Formula: The actual number of atoms of each element in a molecule.

Important Equations

• E = Q, where E is the energy change and Q is the heat energy transferred.
• ΔH = Qp, where ΔH is the enthalpy change and Qp is the heat energy transferred at constant pressure.