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Chem 111 Ch. 3

atomic mass the mass of the atom in atomic mass units (amu)
atomic mass unit (amu) a mass exactly equal to 1/12 the mass of one carbon-12 atom (the carbon isotope that has six protons and six neutrons - 12 amu provides the standard for measuring the atomic mass of other elements)
average atomic mass (percent x 100)(atomic mass of element #1) + (percent x 100)(atomic mass of element #2) = average atomic mass (in amu)
mole (mol) the amount of a substance that contains as many elementary entities (atoms, molecules, or other particles) as there are atoms in exactly 12 g of the carbon-12 isotope (Avogadro's number)
Avogadro's Number (NA) Amedeo Avogadro - accepted value = 6.022 x 10^23
molar mass the mass of 1 mole of units (such as atoms or molecules) of a substance
molecular mass the sum of the atomic masses (in amu) in the molecule
the mass spectrometer most direct and accurate method for determining atomic and molecular masses - pg. 67
percent composition the percent by mass of each element in a compound = [ (n x molar mass of element) / molar mass of compound ] x 100%
calculating an empirical formula of a compound from its percent composition mass percent --> moles of each element --> mole ratios of elements --> empirical formulas
chemical reaction a process in which a substance (or substances) is changed into one or more new substances
chemical equation uses chemical symbols to show what happens during a chemical reaction
Created by: court52