Chapter 03 notes S10

# Chapter 03 notes S10 - 1 Chapter 3 Stoichiometry 2 Atomic...

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1 Chapter 3 Stoichiometry

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2 Atomic Mass Avogadro’s Number and Molar Mass
3 Average Atomic Mass Atomic Mass: Mass of 1 atom in atomic mass units 1 amu =1/12 of the mass of 1 C-12 atom Naturally occurring carbon is a mixture of isotopes 98.90% 6 protons 6 neutrons 12.000amu 1.100% 6 protons 7 neutrons 13.003amu Atomic mass of naturally occurring carbon (0.9890 x 12.000amu)+ (0.0110 x 13.003amu) Atomic Mass of C = 12.01amu 12 6 C 13 6 C

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4 The Mole Mole # of particles in 12g of C-12 Avogadro’s number N a = 6.02 x 10 23 atoms/mol Determined experimentally Similar to the word "dozen” Converts molecules to manageable numbers Allows conversion to mass measurement experimentally 1 atom C-12 = 1.99 x 10 -23 g Makes math more convenient Convert from molecular to real world 1 Mole of each substance
5 Molar Mass Calculations The mass of one mole of a substance Conversion factor between mass and moles (#grams/ 1mole) C-12: Calculations Atomic mass: Listed on periodic table Molecular mass: Addition of atomic masses Formula mass: Addition of masses of ions in a salt Examples: 1 mol Na = 22.99 g/mol 1 mol SO 2 = 64.07g/mol 1 mole NaCl = 58.44g/mol SO 2 NaCl 23 23 6.02 10 1.99 10 12 12 1 1 x atoms x g g x amu mol atom mol - = =

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6 Mole-based Calculations Molar Mass ( M ): grams/mol Avogadro’s Number N a : 6.02x10 23 particles/mol atoms 5.01x10 1mol 6.02x10 x 0.833mol 12.0g 1mol x 10.0g 23 C atoms 23 C C C C = = atoms 5.01x10 x 6.02x10 1mol 0.833mol x 1mol 12.0g 10.0g 23 atoms 23 C C C C C = =
7 Percent Composition of Compounds

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8 Mass Percent Composition Mass of each element per 100g of a compound Chemical formula gives molar amounts Must convert moles to mass in grams Percentage Review General idea for percentages is “part / total” Units should be the same for both values Tips for determining mass percent composition Base everything on 1 mole to find molar mass (total) Don’t forget to multiply mass of each atom by the number of occurrences in molecule (part)
9 Mass % Composition of Calcium Chlorite, Ca(ClO 2 ) 2 Find the molar mass of Ca(ClO 2 ) 2 1 mol Ca x 40.08g/mol Ca = 40.08 g Ca 2 mol Cl x 35.45 g/mol Cl = 70.90 g Cl 4 mol O x 15.99 g/mol O = 64.00 g O

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Chapter 03 notes S10 - 1 Chapter 3 Stoichiometry 2 Atomic...

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