The law of definite proportions, also known as the law of constant composition, states that a chemical compound always contains the same elements in the same proportion by mass. This means that the mass ratio of the constituent elements in a compound is always constant.
For example, water (H2O) consists of two hydrogen atoms and one oxygen atom. Regardless of the source of water, the mass ratio of hydrogen to oxygen is always 2:16, or 1:8. This ratio remains constant whether the water is from a lake, an ocean, or produced in a laboratory.
The law of definite proportions was first formulated by Joseph Proust in the late 18th century and is a fundamental principle in chemistry. It helps determine the chemical formula of a compound based on the masses of its elemental constituents.
law of definite proportions
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