1. Introduction
- The Laws of Chemical Combination describe the fundamental principles that govern chemical reactions.
- These laws were established based on experimental observations.
- The two primary laws are the Law of Conservation of Mass and the Law of Definite Proportions.
2. Law of Conservation of Mass
- Proposed by Antoine Lavoisier in 1789.
- The law states that mass can neither be created nor destroyed in a chemical reaction.
- The total mass of reactants is equal to the total mass of products.
- For example, in the reaction: H₂ + O₂ → H₂O, the total mass of hydrogen and oxygen equals the mass of water formed.
- This law supports the principle of matter conservation.
3. Significance of the Law of Conservation of Mass
- Forms the basis of stoichiometry in chemistry.
- Used in chemical calculations to determine the amount of reactants and products.
- Applicable in both physical and chemical changes.
4. Law of Definite Proportions
- Also known as the Law of Constant Composition.
- Proposed by Joseph Proust in 1799.
- The law states that a chemical compound always contains its constituent elements in a fixed ratio by mass.
- For example, in water (H₂O), the ratio of hydrogen to oxygen by mass is always 2:16 or 1:8.
- Independent of the source or method of preparation, the composition of a compound remains the same.
5. Significance of the Law of Definite Proportions
- Explains the uniformity in the composition of compounds.
- Helps in the study of chemical formulae.
- Forms the foundation for understanding chemical bonding.
6. Applications
- Both laws are essential in chemical engineering, industrial chemistry, and environmental science.
- Used in the analysis and synthesis of chemical compounds.
- Provide the basis for the quantitative study of chemical reactions.
7. Limitations
- The laws are not strictly valid for nuclear reactions, where mass and energy interconvert.
- The Law of Definite Proportions may not hold in non-stoichiometric compounds (e.g., FeO).