# Ch.4 Notes - Chapter 4 Topics Atomic weights and molecular...

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Topics: Atomic weights and molecular weights The mole concept Molar mass of elements and compounds Mass and mole conversions Chemical formulas and percent composition Chemical reactions and equations Balancing Stoichiometry: quantitative relationships in chemical reactions Big Picture: Understanding Chemical Equations 2CH 3 OH + 3O 2 2CO 2 + 4H 2 O Note: Dimensional Analysis (Factor Label Method) is the key problem solving approach The Mole Concept The mole (mol) is the unit for counting in chemistry; it is the chemist’s ‘dozen’ ONE MOLE= 6.022 x 10 23 particles atoms (Avogadro’s number) Stoichiometry: CH4 1 C atom + 4 H atoms Or 1 mol C atoms + 4 mols H atoms Important: for CH4 , conversion factor is 1 mol C/ 4 mols H 4 mols H/ 1 mol C Molar mass of elements Def (SI): 1 mol of Carbon-12 = 12g exactly Molar mass (of element)- Atomic weight of an element expressed in grams (of grams/mole) Contains 6.022 x 10 23 atoms (Avogadro’s number) O 16.0 g/mol C 12.01 g/mol Quality (g) Moles Atoms 16.0 g O 1.00 mol O 6.022 x 10 23 O atoms 12.01 g C 1.00 mol O 6.022 x 10 23 C atoms 19.0 g F 1.00 mol F 6.022 x 10 23 F atoms 8.0 g O 0.50 mol O 3.011 x 10 23 O atoms 32.0 g O 2.00 mol O 1.204 x 10 24 O atoms 196.967 g Au 1.00 mol Au 6.022 x 10 23 Au atoms Conversion Factors: 1 mol O = 16.0 g O 1 mol O = 6.022 x 10 23 O atoms

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Ch.4 Notes - Chapter 4 Topics Atomic weights and molecular...

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