Law of combining weights

I cu ft of O2 10 form only 2 cubic feet of HiO. This relationship is based on Avogadro s law and the law of combining weights. 

STOICHIOMETRY. The mathematics of chemical reactions and processes. It relates to all the quantitative aspects of chemical changes, both mass and energy Stoichiometry is based on file absolute laws of conversion of mass and of energy and on the chemical law of combining weights. This basis makes stoichiometry as exact as any other branch of mathematics. 

The law of combining weights may be stated as follows For every element a combining weight may be chosen such that in all pure compound substances the ratio of the number of combining weights of the different elements is the ratio of simple integrals. 

The Law.of Combining Weights. The weights of two elements (or simple multiples of these weights) which react with the same weight of a third element may also react with each other. 

Elements and Compounds—Chemical Symbols—Molecules—Atoms —Electrons—How Electrons Form Atoms—Explanation of Chemical Activity—Chemical Formulas—Speed of Chemical Reactions—Physical and Chemical Changes—The Law of Definite Proportions—Different Kinds of Chemical Reaction —Classification of Chemical Compounds—The Law of Combining Weights—Solutions—Acids and Bases—Neutral Substances—Organic and Inorganic Chemistry—Electrochemistry —Experiments in Electrochemistry, Pages 7-39... 

Following Lavoisier, chemists had a set of rules and a provisional list of elements to work with. Later, using Dalton s atomic theory and his laws of combining proportions, chemists were able to determine atomic weights and to arrive at molecular formulas indicating the nature and number of the atoms in a molecule. Molecules, the smallest part of a compound that possessed the chemical properties of that compound, could then be classified. Berzelius s classification of mineral compounds rested upon his discoveries about the electrochemical properties of atoms, an explanatory notion grafted onto Dalton s simple atomic theory. Chemists were able to establish research programs based... 

Italian chemist and physicist Amadeo Avogadro (1776-1856) proposed a correct molecular explanation for Gay-Lussac s law of combining volumes. His work provided a simple way to determine atomic weights and molecular weights of gases. 

Subsequent research proved that Gay-Lussac s Law of Combining Volumes is not exact, but only an approximation,4 so that oxygen and hydrogen do not behave as perfect gases. For an accurate calculation of the relative values for the atomic weights of hydrogen and oxygen, it is therefore essential to know not only the relative densities of the... 

Three laws of stoichiometry may now be considered The Laio of Constant Proportions, The Law of Simple Multiple Proportions, and The Law of Combining V/eights. These were originally empirical laws, based upon experiment. At the time that the laws were formulated it was seen that the atomic theory provides a simple explanation of them and although the laws do not require that the atomic theory be true most chemists accepted the theory as providing the simplest explanation of chemical weight relations. 

Berzelius then set about determining atomic weights with more sophistication than Dalton had been able to do. In this project, Berzelius made use of the findings of Dulong and Petit and of Mitscher-lich, as well as of Gay-Lussac s law of combining volumes. (He did not, however, use Avogadro s hypothesis.) Berzelius s first table of atomic weights, published in 1828, compares favorably, for all but two or three elements, with the accepted values of today. 

Aquivalent, n. equivalent, gesetz, n. law of equivalents, -gewicht, n. equivalent weight, combining weight, -leiffilhigkeit, /. equivalent conductivity, -verhaltnis, n. equivalent proportion ratio of equivalents. 

This success of the atomic theory is not surprising to a historian of science. The atomic theory was first deduced from the laws of chemical composition. In the first decade of the nineteenth century, an English scientist named John Dalton wondered why chemical compounds display such simple weight relations. He proposed that perhaps each element consists of discrete particles and perhaps each compound is composed of molecules that can be formed only by a unique combination of these particles. Suddenly many facts of chemistry became understandable in terms of this proposal. The continued success of the atomic theory in correlating a multitude of new observations accounts for its survival. Today, many other types of evidence can be cited to support the atomic postulate, but the laws of chemical composition still provide the cornerstone for our belief in this theory of the structure of matter. 

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