Chemical Engineering Tips – Moles

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In October 1971, at the 14th General Conference on Weights and Measures, attended by 41 countries, the seventh base unit of the International System of Units was officially adopted – the mole. Mole is the ’amount of substance’ of a system (also known as a material system), where the number of elementary units contained in that system is equal to the number of atoms in 0.012 kg of carbon-12; this quantity is called 1 mol. Because the number of carbon atoms in 0.012 kg of carbon-12 is equal to Avogadro’s number. Therefore, 1 mol of any substance contains Avogadro’s number of elementary units. The basic units that make up substances can be particles such as atoms, molecules, ions, electrons, protons, neutrons, etc., or specific combinations of these particles. “\"Amount of substance,\" like length and mass, is a physical quantity; it is a quantity used specifically to indicate the number of basic units of a substance. And mole is the unit of \"amount of substance\". In the International System of Units, it is designated by the name mole, with the symbol mol. When using the “mole” unit, it is necessary to specify the basic unit that makes up the substance, writing the name of that basic unit after the mole: for example, 1 mole of hydrogen atoms or 1 mol H. 　 0.5 moles of chloride ions or 0.5 mol Cl-. 　 2 moles of sulfuric acid or 2 mol H2SO4.