The Great Dictionary of the word equivalent (Latin sounds like aequivalens) explains how something equivalent, or equivalent is an equivalent to another that it will be able to completely replace.In chemistry, the law of equivalents (used since the late 18th century, it is taught in school, chemists and biologists are used in different countries in theory and in practice) stipulates that all chemicals react in proportion to their equivalents.Open the law was a German chemist I. Richter, whose works have long been known.In his three-volume work published in the period from 1792 to 1794 years, entitled "Beginnings of stoichiometry, or a method of measuring the chemical elements", the scientists showed that the chemicals react in a strict ratio.They also introduced a term such as "stoichiometry".Now it is a branch of chemistry that describes the ratio of the reactants entering into a chemical reaction.
Richter first in his works brought quantitative reaction equations.They are conditional entry that contains qualitative and quantitative information about the processes occurring in the interaction of different chemicals called reagents.Even during the alchemical science to refer to simple elements, scientists use different symbols, it was later discovered the formula of complex (consisting of several elements) chemicals.But Richter IV (under the influence of his teacher and philosopher Immanuel Kant, who claimed that the individual areas of Natural Sciences contain as much true science as there is mathematics in it) used in the thesis and the chemical formulas of the term "stoichiometry", described the quantitative reaction equationand discovered the law of equivalents.The formula expressing its can be written: E2 • m1 = A1 • m2.Where m1 and m2 - is the mass of substance "1" and "2", unreacted, and A1 and A2 - are their chemical equivalents.
To understand the law of equivalents, it is necessary to clarify that the equivalent - is conditional, or the actual number of substances that can attach hydrogen cation in the acid-base reaction or an electron as a result of redox reactions.Equivalent mass - is the mass of one equivalent.It is believed that one equivalent reacts substance (or displaces) to one gram of hydrogen or oxygen with 8 grams or 35.5 grams of chlorine.In practice, the amount of substance equivalent frequently has a very small size, so it is usually expressed in moles.In one mole contains a constant amount of particles (atoms, ions or molecules), it is the number of Avogadro: NA = 6,02214179 (30) · 1023.Weight of one mole of a substance in grams which is numerically equal to its weight in atomic mass units.
Based on the law of equivalents, it can be argued that the acid-base titration, flowing through the reaction equation: KOH + HCl → KCl + H2O, the interaction of one mole of potassium hydroxide with 1 mole of hydrochloric acid to give 1 mole of salt, called chloridepotassium, and 1 mole of water.That is the equivalent weight of potassium hydroxide is equal to E KOH = 39 + 16 + 1 = 56 g hydrochloric acid - E HCl = 1 + 35 = 36 g, potassium chloride - E KCl = 39 + 35 = 74 g, water - E H2O =• 2 1 + 16 = 18 In order that completely neutralize 56 g of potassium hydroxide necessary to 36g HCl.The result will be 74 g of potassium chloride and 18 g of water.But since the law established that the mass of substances, unreacted proportional cash equivalents, knowing the amount of one reagent can count how will react the second reactant or calculate yield.
example, as will potassium chloride, if it is known that hydrochloric acid was completely neutralized by 100 g of potassium hydroxide?Using the law of equivalents, can be written: 56 • mKCl = 74 • 100. Then mKCl = (74 • 100) / 56 = 132, the A hydrochloric acid to neutralize the potassium hydroxide 100 g If you need a 64 100 g potassium hydroxide to neutralize the sulfuric acid:2KOH + H2SO4 → K2SO4 + 2H2O, this would require a very different amount of acid.As indicated by the stoichiometric coefficients of this reaction, 2 moles of potassium hydroxide react one mole of sulfuric acid, and the result will be one mole of potassium sulfate and two moles of water.Knowing that the mass of the substances reacted proportional equivalent weights can be written: 2 • 56 • 98 • mH2SO4 = 100, then 100 to neutralize the potassium hydroxide required mH2SO4 = 88 g of sulfuric acid.This produces 155 g of potassium sulfate.The amount of water allocated to the neutralization of 100 g of potassium hydroxide, hydrochloric acid or sulfuric acid, is the same and equal to '32
apply the law equivalents chemistry (analytical, inorganic, organic, etc.) for the study materials and other experiments basedbased on the balance of chemical reactions.In addition, it is used (for preparation of material balances) in the design and operation of the laboratory, pilot or industrial installations intended for synthesis of chemicals.They always use specialists chemical, medical, biological, sanitary and epidemiological laboratories, as it is the basis of the formulas by which the computation is carried out many test results.
