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Law of Multiple Proportions

The Law of Multiple Proportions, or Dalton's Law, is a primary law of stoichiometry. It states that if two elements form multiple compounds, the ratios of the masses of the second element combining with a fixed mass of the first elements will be in ratios of small whole numbers.

For example, the oxygen compared between CO and CO₂ has a simple 1:2 ratio; one oxygen in the first compound, two oxygen in the second compound. 100 grams of carbon will react with either 133 grams of oxygen to produce carbon monoxide, or with 266 grams of oxygen to produce carbon dioxide.

This law, composed by John Dalton based on the law of definite proportions, was part of what laid the groundwork for his atomic theory, and for the basis of chemical formulas for compounds.

Though the proportions can get quite complex, as with large hydrocarbon molecules, it holds true with great accuracy. Some numbers in large molecules get very large, but the ratios are always whole numbers to whole numbers.

Web Resources On Law of Multiple Proportions

Fact Monster: law of simple multiple proportions
Law of Multiple Proportions

Book Resources On Law of Multiple Proportions

Chemistry: Matter and Its Changes by Brady & Senese
Shaum's Outline Of General, Organic and Biological Chemistry by Odian & Blei

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