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CHEM CH. 3
Chem 111 Ch. 3
| Question | Answer |
|---|---|
| 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 |
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