Just as 1 mol of atoms contains 6.022 × 10 23 atoms, 1 mol of eggs contains 6.022 × 10 23 eggs. According to the most recent experimental measurements, this mass of carbon-12 contains 6.022142 × 10 23 atoms, but for most purposes 6.022 × 10 23 provides an adequate number of significant figures. The mole is used for this purpose.Ī mole is defined as the amount of a substance that contains the number of carbon atoms in exactly 12 g of isotopically pure carbon-12. Any readily measurable mass of an element or compound contains an extraordinarily large number of atoms, molecules, or ions, so an extraordinarily large numerical unit is needed to count them. Atoms are so small, however, that even 500 atoms are too small to see or measure by most common techniques. Sheets of printer paper are packaged in reams of 500, a seemingly large number. For example, cans of soda come in a six-pack, eggs are sold by the dozen (12), and pencils often come in a gross (12 dozen, or 144). Many familiar items are sold in numerical quantities that have unusual names. The quantity of a substance that contains the same number of units (e.g., atoms or molecules) as the number of carbon atoms in exactly 12 g of isotopically pure carbon-12., from the Latin moles, meaning “pile” or “heap” ( not from the small subterranean animal!). The unit that provides this link is the mole (mol). To analyze the transformations that occur between individual atoms or molecules in a chemical reaction it is therefore absolutely essential for chemists to know how many atoms or molecules are contained in a measurable quantity in the laboratory-a given mass of sample. In the laboratory, for example, the masses of compounds and elements used by chemists typically range from milligrams to grams, while in industry, chemicals are bought and sold in kilograms and tons. Because the masses of individual atoms are so minuscule (on the order of 10 −23 g/atom), chemists do not measure the mass of individual atoms or molecules. The problem for Dalton and other early chemists was to discover the quantitative relationship between the number of atoms in a chemical substance and its mass. We also described the law of multiple proportions, which states that the ratios of the masses of elements that form a series of compounds are small whole numbers. In Dalton’s theory each chemical compound has a particular combination of atoms and that the ratios of the numbers of atoms of the elements present are usually small whole numbers. The same calculation can also be done in a tabular format, which is especially helpful for more complex molecules: This molar mass calculator can only handle two bracket levels at a time.\right ) \right ] \) Tricalcium phosphate would be entered as Ca3(PO4)2.
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For example, calcium carbonate would be entered as CaCO3, not caco3. The chemical formula should be entered using standard format. This calculator is a convenient tool for calculating the molar mass of chemical compounds in lieu of using a periodic table. These include consumption of pH adjustment chemicals for RO feedwater, solubilities of scale forming compounds in reverse osmosis systems, and cation rejection calculations using charge balance (meq/l) in nanofiltration systems. Many other calculations require conversion into moles.
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Knowing the desired concentration of ClO2, the system integrator can calculate the consumption of each of the reactants using the stoichiometric relationship:ĢNaClO2 + NaOCl + 2HCl ↔ 2ClO2 + H2O + 3NaCl For example, certain types of chlorine dioxide (ClO2) generators would use sodium hypochlorite (NaOCl), sodium chlorite (NaClO2) and hydrochloric acid (HCl). When calculating consumption of certain RO chemicals for reverse osmosis pretreatment or post-treatment, it is often necessary to convert into moles.