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concentration

   Also found in: Dictionary/thesaurus, Medical, Acronyms, Wikipedia, Hutchinson 0.03 sec.
concentration, in chemistry, measure of the relative proportions of two or more quantities in a mixture mixture, in chemistry, a physical combination of two or more pure substances (i.e., elements or compounds). A mixture is distinguished from a compound, which is formed by the chemical combination of two or more pure substances in a fixed, definite proportion.
..... Click the link for more information. . The concentration of a solute is very important in studying chemical reactions because it determines how often molecules collide in solution and thus indirectly determines the rates of reactions and the conditions at equilibrium (see chemical equilibrium chemical equilibrium, state of balance in which two opposing reversible chemical reactions proceed at constant equal rates with no net change in the system. For example, when hydrogen gas, H2, and iodine gas, I2
..... Click the link for more information. ).

Concentration may be expressed in a number of ways. The simplest statement of the concentrations of the components of a mixture is in terms of their percentages by weight or volume. Mixtures of solids or liquids are frequently specified by weight percentage concentrations, such as alloys of metals or mixtures used in cooking, whereas mixtures of gases are usually specified by volume percentages. Very low concentrations may be expressed in parts per million (ppm), as in specifying the relative presence of various substances in the atmosphere.

In addition to these means of expressing concentration, several others are defined especially for describing solutions solution, in chemistry, homogeneous mixture of two or more substances. The dissolving medium is called the solvent , and the dissolved material is called the solute. A solution is distinct from a colloid or a suspension .
..... Click the link for more information. : molarity, molality, mole fraction, formality, and normality. Some of these define the concentration of the solute in reference to the amount of solvent, others in reference to the total amount of solution. The molarity of a solution is the number of moles mole, in chemistry, a quantity of particles of any type equal to Avogadro's number, or 6.02×1023 particles. One gram-molecular weight of any molecular substance contains exactly one mole of molecules.
..... Click the link for more information.  of solute per liter of solution; e.g., a solution of glucose in water containing 180.16 grams (1 gram-molecular weight, or mole) of glucose per liter of solution is referred to as one molar (1 M). The molality of a solution is the number of moles of solute per 1,000 grams of solvent; a solution prepared by dissolving 180.16 grams of glucose in 1,000 grams of water is one molal (1 m). The mole fraction of a solution is the ratio of moles of solute to the total number of moles in the solution. Since ionic compounds, such as sodium chloride, NaCl, do not occur as molecules, their concentrations cannot be expressed in terms of molarity, molality, or mole fraction. Instead, the concentration of an ionic compound in solution may be given by its formality, the number of gram-formula weights of the compound per liter of solution; e.g., a solution containing 58.44 grams (one gram-formula weight) of NaCl per liter of solution is one formal (1 F). In considering the reactions of certain solutions in combination, for example the neutralization neutralization, chemical reaction, according to the Arrhenius theory of acids and bases , in which a water solution of acid is mixed with a water solution of base to form a salt and water; this reaction is complete only if the resulting solution has neither acidic
..... Click the link for more information.  of acids and bases, a useful expression of the concentration is the normality of each solution, the number of gram-equivalent weights of solute per liter of solution (see equivalent weight equivalent weight. The equivalent weight of an element or radical is equal to its atomic weight or formula weight divided by the valence it assumes in compounds.
..... Click the link for more information. ); e.g., a solution containing 49.04 grams (one gram-equivalent weight) of sulfuric acid, H2SO4, per liter of solution is one normal (1 N). Concentrations of solutions may also frequently be given in terms of the weight of solute in a given volume of solvent or solution.

In communications, the combining of multiple channels into one.



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Stripped of a great deal of somewhat obscure metaphysical theory, this distinction reduced itself to the certainly vital one, with which all true criticism more or less directly has to do, between the lower and higher degrees of intensity in the [94] poet's conception of his subject, and his concentration of himself upon his work.
The Guardian by Pater, Walter Horatio View in context
It proved, incontrovertibly, the disastrous effects of machinery and division of labour; the concentration of capital and land in a few hands; overproduction and crises; it pointed out the inevitable ruin of the petty bourgeois and peasant, the misery of the proletariat, the anarchy in production, the crying inequalities in the distribution of wealth, the industrial war of extermination between nations, the dissolution of old moral bonds, of the old family relations, of the old nationalities.
The Communist Manifesto by Marx, Karl & Engles, Frederick View in context
Yet when due respect has been paid to this critic of old time, the fact still remains that concentration and suggestion are the two essentials of Chinese poetry.
A Lute of Jade by Cranmer-Byng, L. View in context
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