EQUIVALENT

From Big Medical Encyclopedia

EQUIVALENT x and m and the p e about a cue. AA. shows what quantity of gram atoms of an element attaches or replaces with 1 Ghat of hydrogen. The equivalent is used for expression of concentration (see) substances not only in solutions, but also in biological liquids, cells and fabrics.

All substances interact with each other in strictly certain quantities proportional them E. (law of equivalents). For the elements which are not interacting with hydrogen, AA. determine indirectly — by structure of connections with any other element, AA. to-rogo it is known (e.g., with oxygen). Mass of one E. (equivalent weight), expressed in grams, the gram-ekvivalentokhm is called (Mrs.); 1 Mrs. it is in number equal to the relation of atomic weight (weight) of an element to its valency in this connection. So, the chemical equivalent of oxygen is equal in the H20 connection to 1/2 mol, and the gram equivalent is equal to 8 g, the chemical equivalent of iron is equal in the Fe203 connection to 1/3 mol, and the gram equivalent is equal to 18,6 g the Chemical equivalent of chlorine, proceeding from the HC1 connection, 1 mol is equal. Many elements form on some connections with any other element and have a number of various values of a chemical equivalent in gram equivalents, but in all cases these values belong among themselves as simple integers (law of multiple proportions).


The number of grams equivalents of substance which is contained in 1 l of solution is called normality of solution. Sometimes along with equivalent weight use the concept «equivalent volume», i.e. the volume occupied under existing conditions by one chemical equivalent of substance. The term «chemical equivalent» extends also to difficult connections like acids and the bases (see) and salts (see). The equivalent mass of such substances is defined by the relation a pier. the weight (weight) to acid value, basicity or the sum of charges of cations (anions) respectively. AA. oxidizers and reducers it is equal to number of the electrons participating in the corresponding oxidation reactions — recovery (see Ocky-sliteljno-recover telny reactions). In electrochemistry there is a concept «electrochemical equivalent», the Crimea is defined amount of the substance undergoing chemical transformation on electrodes during the passing through electrolyte 1 to (one pendent) of electricity. In number electrochemical equivalent is equal private from division of size of a chemical equivalent into number of transfer (a share of the electricity transferred by ions of this type). Bibliography: Glinka N. L. General chemistry, page 29, M., 1983. V. A. Pekkel.

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