3-A - C h a p t e r Chemistry 5 th Edition McMurry/Fay 3...

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Unformatted text preview: C h a p t e r Chemistry, 5 th Edition McMurry/Fay 3 Formulas, Equations, and Moles 2 The Structure of Atoms Atomic Mass Unit 1 amu = 1/12 of the mass of on atom of Carbon-12 1 amu = 1.6605 x 10-24 g 3 Mass: proton = 1.00728 amu neutron = 1.0086 amu electron = 0.0005486 12 C atom = 12.00000 amu 13 C atom = 13.00335 amu Atomic and Molecular Mass 1 amu = mass of carbon- 12 atom 12 4 Atomic and Molecular Mass • The atomic masses as tabulated in the periodic table are the averages of the naturally occurring isotopes. • Mass of C = average of 12 C and 13 C = 0.9889 x 12 amu + 0.0111 x 13.0034 amu = 12.011 amu 5 Atomic and Molecular Mass The mass of a molecule is just the sum of the masses of m(C 2 H 4 O 2 ) = 2·m C + 4·m H + 2·m O = 2·(12.01) + 4·(1.01) + 2·(16.00) = 60.06 amu 6 Avogadro and the Mole • One mole of a substance is the gram mass value equal to the amu mass of the substance. • One mole of any substance contains 6.02 x 10 23 units of that substance. • Avogadro’s Number (N A , 6.022 x 10 23 ) is the numerical value assigned to the unit, 1 mole. 7 Avogadro and the Mole 8 Avogadro and the Mole • Methionine, an amino acid used by organisms to make proteins, is represented below. Write the formula for methionine and calculate its molar mass. (red = O; gray = C; blue = N; yellow = S; ivory = H) 9 Avogadro and the Mole • The Mole: Allows us to make comparisons between substances that have different masses. 10 Balancing Chemical Equations • A balanced chemical equation represents the conversion of the reactants to products such that the number of atoms of each element is conserved. reactants → products limestone → quicklime + gas Calcium carbonate → calcium oxide + carbon dioxide CaCO 3 (s) → CaO (s) + CO 2 (g) 11 Balancing Chemical Equations CaCO 3 (s) → CaO (s) + CO 2 (g) The letters in parentheses following each substance are called State Symbols (g) → gas (l) → liquid (s) → solid (aq) → aqueous 12 Balancing Chemical Equations A balanced equation MUST have the same number of atoms of each element on both sides of the equation. H 2 + O 2 → H 2 O Not Balanced H 2 + ½O 2 → H 2 O Balanced 2H 2 + O 2 → 2H 2 O Balanced 13 Balancing Chemical Equations The numbers multiplying chemical formulas in a chemical equation are called: Stoichiometric Coefficients (S.C.) 2H 2 + O 2 → 2H 2 O Balanced Here 2, 1, and 2 are stoichiometric coefficients. 14 Balancing Chemical Equations Hints for Balancing Chemical Equations:...
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3-A - C h a p t e r Chemistry 5 th Edition McMurry/Fay 3...

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