What is a mole and why do we use it; what is molar mass; step by step tutorial explaining how to convert mole-mass and mass-mole and how to use the periodic table for determination of molar mass; mole-particle and particle-mole conversions explained; mass-particle and particle-mass conversions explained using a dimensional analysis approach.
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— More on the Mole | Wiki —
"The mole is the unit of measurement in the International System of Units (SI) for amount of substance. It is defined as the amount of a chemical substance that contains as many elementary entities, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of carbon-12 (12C), the isotope of carbon with relative atomic mass 12 by definition. This number is expressed by the Avogadro constant, which has a value of 6.022140857(74)×1023 mol-1. The mole is one of the base units of the SI, and has the unit symbol mol.
The mole is widely used in chemistry as a convenient way to express amounts of reactants and products of chemical reactions. For example, the chemical equation 2 H2 + O2 → 2 H2O implies that 2 mol of dihydrogen (H2) and 1 mol of dioxygen (O2) react to form 2 mol of water (H2O). The mole may also be used to express the number of atoms, ions, or other elementary entities in a given sample of any substance. The concentration of a solution is commonly expressed by its molarity, defined as the number of moles of the dissolved substance per litre of solution.
While according to the official SI definition, the words "mol(es) of" should be followed by a singular word denoting a substance ("water", "oxygen"), they are commonly used by chemists with a plural word referring to elementary entities, such as atoms or electrons. In this usage, mole is a number equal to 0.6022 trillion trillions, i.e. Avogadro's number. The expression "mol(es) of electrons", widely used in electrochemistry, is particularly incompatible with the SI definition since there is no 'electron substance' whose amount could be quantified.
The number of molecules per mole is known as Avogadro's constant, and is defined such that the mass of one mole of a substance, expressed in grams, is equal to the mean relative molecular mass of the substance. For example, the mean relative molecular mass of natural water is about 18.015, therefore, one mole of water has a mass of about 18.015 grams.
The term gram-molecule was formerly used for essentially the same concept. The term gram-atom has been used for a related but distinct concept, namely a quantity of a substance that contains Avogadro's number of atoms, whether isolated or combined in molecules. Thus, for example, 1 mole of MgB2 is 1 gram-molecule of MgB2 but 3 gram-atoms of MgB2.
In honor of the unit, some chemists celebrate October 23, which is a reference to the 1023 scale of the Avogadro constant, as "Mole Day". Some also do the same for February 6 and June 2."
Wikipedia contributors. "Mole (unit)." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 27 Jun. 2016. Web. 2 Jul. 2016.