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chapt03_lec

# chapt03_lec - Chapter 3 Stoichiometry 3-1 Dr Wolfs CHM 101...

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3-1 Dr. Wolf’s CHM 101 Chapter 3 Stoichiometry

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3-2 Dr. Wolf’s CHM 101 Mole - Mass Relationships in Chemical Systems 3.5 Fundamentals of Solution Stoichiometry 3.1 The Mole 3.2 Determining the Formula of an Unknown Compound 3.3 Writing and Balancing Chemical Equations 3.4 Calculating the Amounts of Reactant and Product
3-3 Dr. Wolf’s CHM 101 mole - the amount of a substance that contains the same number of entities as there are atoms in exactly 12g of carbon-12, i.e. the numerical value of the atom’s mass in grams This amount is 6.022x10 23 . The number is called Avogadro’s number and is abbrieviated as N. One mole (1 mol) contains 6.022x10 23 entities (to four significant figures) The Mole

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3-4 Dr. Wolf’s CHM 101 Counting Objects of Fixed Relative Mass 12 red marbles @ 7g each = 84g 12 yellow marbles @4g each=48g So equal numbers will always have the same 7:4 ratio = 84:48 55.85g Fe = 6.022 x 10 23 atoms Fe 32.07g S = 6.022 x 10 23 atoms S These values come from the atomic mass values for Fe and S in the Periodic Table
3-5 Dr. Wolf’s CHM 101 Water, H 2 O 18.02 g One Mole of Common Substances CaCO 3 100.09 g Oxygen, O 2 32.00 g Copper 63.55 g

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3-6 Dr. Wolf’s CHM 101 Table 3.1 Summary of Mass Terminology Term Definition Unit Isotopic mass Mass of an isotope of an element amu Atomic mass Molecular (or formula) mass Molar mass ( M ) (also called atomic weight) (also called molecular weight) (also called gram-molecular weight) amu amu g/mol Average of the masses of the naturally occurring isotopes of an element weighted according to their abundance Sum of the atomic masses of the atoms (or ions) in a molecule (or formula unit) Mass of 1 mole of chemical entities (atoms, ions, molecules, formula units)
3-7 Dr. Wolf’s CHM 101 Calculating the Molar Mass of a Substance For monatomic elements, the molar mass is the numerical value on the periodic table expressed in g/mol For molecules, the molar mass is the sum of the molar masses of each of the atoms in the molecular formula.

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3-8 Dr. Wolf’s CHM 101 Information Contained in the Chemical Formula of Glucose C 6 H 12 O 6 ( M = 180.16 g/mol) Oxygen (O) Mass/mole of compound 6 atoms 96.00 g Carbon (C) Hydrogen (H) Atoms/molecule of compound Moles of atoms/ mole of compound Atoms/mole of compound Mass/molecule of compound 6 atoms 12 atoms 6 moles of atoms 12 moles of atoms 6 moles of atoms 6(6.022 x 10 23 ) atoms 12(6.022 x 10 23 ) atoms 6(6.022 x 10 23 ) atoms 6(12.01 amu) =72.06 amu 12(1.008 amu) =12.10 amu 6(16.00 amu) =96.00 amu 72.06 g 12.10 g So for glucose with 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atom, the molar mass is 72.06 + 12.10 + 96.00 = 180.16 g/mol
3-9 Dr. Wolf’s CHM 101 Interconverting Moles, Mass, and Number of Chemical Entities Mass (g) = no. of moles x no. of grams 1 mol No. of moles = mass (g) x no. of grams 1 mol No. of entities = no. of moles x 6.022x10 23 entities 1 mol No. of moles = no. of entities x 6.022x10 23 entities 1 mol

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3-10 Dr. Wolf’s CHM 101
3-11 Dr. Wolf’s CHM 101 Sample Problem 3.1 Calculating the Mass and the Number of Atoms in a Given Number of Moles of an Element PROBLEM: PLAN: SOLUTION: amount(mol) of Ag mass(g) of Ag (a) Silver (Ag) is used in jewelry and tableware but no longer in U.S.

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