Law of definite proportions

Definition

The Law of Definite Proportions states that a chemical compound always contains exactly the same proportion of elements by mass. This principle is fundamental in understanding the composition of compounds.

5 Must Know Facts For Your Next Test

1. First formulated by Joseph Proust in 1799.
2. Also known as Proust's Law.
3. It applies to pure chemical compounds, not mixtures.
4. Confirms that regardless of the sample size or source, the elemental composition remains constant.
5. Supports the concept of atoms combining in fixed ratios to form compounds.

Review Questions

Related terms

Law of Multiple Proportions:

When 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.

Atomic Theory:

A scientific theory stating that matter is composed of discrete units called atoms.

Chemical Compound: A substance formed from two or more elements chemically united in fixed proportions.