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Definitions Ch 8

Exam 4

Atomic mass unit amu Small unit used to describe the mass of an atom.
Average atomic mass It means that any sample of C can be treated as it were made up of identical carbon atoms.
Mole Unit use to measure the amount of a chemical substance. It helps to convert from particles to mass of a substance. The number of atoms present in 12.01 g of C
Avogandro's number One mole of something is 6.022 x 10^23 units of that substance.(Symbol N) Ex. A mole of water is 6.022 x 10^23 H2O molecules.
Molar mass/ Molecular weigh T: Sum of the atomic masses of each element in a formula B: The mass of 1 mol of the substance (g) (MM)... Remember diatomic elements and count 2 times.
Formula weight Sometimes used to name the molar mass for ionic compounds like NaCl.
Percent composition Gives the mass % of each element in a substance. Formula: Divide the total mass of an element by the total mass of the molecule and then multiply by 100.
Empirical Formula (Simplest formula) The smallest whole-number ratio of elements in a formula. Can be the same for various compounds.
Molecular Formula T: multiple of the empirical formula. B: Gives the composition of the molecules that are present in a compound(Without simplifying).
Created by: lesliemelissa19



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