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Mole

Mole

In chemistry, a mole is a certain number of particles, usually of atoms or molecules. In theory, one could use any number of different terms for counting particles in chemistry. For example, one could talk about a dozen (12) particles or a gross (144) of particles. The problem with these terms is that they describe far fewer particles than one usually encounters in chemistry. Even the tiniest speck of sodium chloride (table salt), for example, contains trillions and trillions of particles.

The term mole, by contrast, refers to 6.022137 × 1023 particles. Written out in the long form, it's 602,213,700,000,000,000,000,000 particles. This number is very special in chemistry and is given the name Avogadro's number, in honor of Italian chemist and physicist Amadeo Avogadro (17761856), who first suggested the concept of a molecule.

A unit like the mole (abbreviated mol) is needed because of the way chemists work with and think about matter. When chemists work in the laboratory, they typically handle a few grams of a substance. They might mix 15 grams of sodium with 15 grams of chlorine. But when substances react with each other, they don't do so by weight. That is, one gram of sodium does not react exactly with one gram of chlorine.

Instead, substances react with each other atom-by-atom or molecule-by-molecule. In the above example, one atom of sodium combines with one atom of chlorine. This ratio is not the same as the weight ratio because one atom of sodium weighs only half as much as one atom of chlorine.

The mole unit, then, acts as a bridge between the level on which chemists actually work in the laboratory (by weight, in grams) and the way substances actually react with each other (by individual particles, such as atoms). One mole of any substanceno matter what substance it isalways contains the same number of particles: the Avogadro number of particles.

Think of what this means in the reaction between sodium and chlorine. If a chemist wants this reaction to occur completely, then exactly the same number of particles of each must be added to the mixture. That is, the same number of moles of each must be used. One can say: 1 mole of sodium will react completely with 1 mole of chlorine. It's easy to calculate a mole of sodium; it is the atomic weight of sodium (22.98977) expressed in grams. And it's easy to calculate a mole of chlorine; it is the molecular weight of chlorine (70.906) expressed in grams. This conversion allows the chemist to weigh out exactly the right amount of sodium and chlorine to make sure the reaction between the two elements goes to completion.

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mole (in chemistry)

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. The term mole is often used in place of gram-molecular weight; e.g., one speaks of 18 grams of water as one mole of water rather than as one gram-molecular weight of water. The mole is a unit in the International System of Units (SI).

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"mole (in chemistry)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 17 Oct. 2017 <http://www.encyclopedia.com>.

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mole

mole Symbol mol. The SI unit of amount of substance. It is equal to the amount of substance that contains as many elementary units as there are atoms in 0.012 kg of carbon–12. The elementary units may be atoms, molecules, ions, radicals, electrons, etc., and must be specified. 1 mole of a compound has a mass equal to its relative molecular mass expressed in grams.

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"mole." A Dictionary of Biology. . Encyclopedia.com. 17 Oct. 2017 <http://www.encyclopedia.com>.

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mole

mole The amount of a substance containing as many elementary units as there are carbon atoms in 12 g of carbon-12 (i.e. the Avogadro number). The elementary units by which the amount of substance is being measured may be atoms, molecules, ions, electrons, radicals, or any other expressly named constituent.

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"mole." A Dictionary of Earth Sciences. . Encyclopedia.com. 17 Oct. 2017 <http://www.encyclopedia.com>.

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mole

mole (symbol mol) SI unit of amount of substance. This is the amount of substance that contains as many elementary units, such as atoms and molecules, as there are atoms in 0.012kg of carbon-12. A mass of one mole of a compound is its relative molecular mass (molecular weight) in grams.

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"mole." World Encyclopedia. . Encyclopedia.com. 17 Oct. 2017 <http://www.encyclopedia.com>.

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mole

mole
1. Mexican; sauce made from sweet pepper, avocado, tomato, and sesame, flavoured with aniseed, garlic, coriander, cinnamon, cloves, chilli, and grated chocolate.

2. Chemical term (abbreviated to mol), 1 mol of a compound is equivalent to its molecular mass in grams.

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"mole." A Dictionary of Food and Nutrition. . Encyclopedia.com. 17 Oct. 2017 <http://www.encyclopedia.com>.

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"mole." A Dictionary of Food and Nutrition. . Retrieved October 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/mole