Laws of Conservation, Constant & Multiple Proportions

Introduction to Chemical Laws

Chemical reactions follow specific laws that help us understand how substances interact. These laws include the Law of Conservation of Mass, the Law of Constant Composition, and the Law of Multiple Proportions.

Law of Conservation of Mass

• This law states that mass is neither created nor destroyed in a chemical reaction.
• The total mass of reactants equals the total mass of products.

Example: When 2 g of hydrogen reacts with 16 g of oxygen, 18 g of water is formed.

Law of Constant Composition

• Also known as the Law of Definite Proportions.
• A chemical compound always contains the same elements in the same proportion by mass.

Example: Water (H₂O) always consists of 2 parts hydrogen and 16 parts oxygen by mass.

Law of Multiple Proportions

• If two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Example: Carbon and oxygen form CO and CO₂. For a fixed mass of carbon, the ratio of the masses of oxygen is 1:2.