9.4 – NOTES Avogadro and Density

V. Stoichiometry involving Avogadro’s number and density A. One fraction could involve the conversion factor 1 mole=6.02 x 1023 particles Example: How many molecules of carbon dioxide are formed when 50.0 grams of methane are burned in air? CH4 + 2O2  CO2 + 2H2O Given: 50.0 g CH4 (16.0g/mol) Find: molecules CO2   50.0 g CH4 x 1 mol CH4 x 1 mol CO2 x 6.02 x 1023 molecules 16.0 g CH4 1 mol CH4 1 mol CO2 = 1.88 x 1024 m-c

B. One fraction could involve the density of a reactant or product. Example: If you burn 1.00 L of octane in your car, how many moles of carbon dioxide are generated? The density of octane is 0.789 g/mL. 2C8H18 + 25O2  16CO2 + 18H2O Given: 1.00L C8H18 (114.2 g/mol) Find: mole CO2   1000mL C8H18 x 0.789g C8H18 x 1 mol C8H18 x 16 mol CO2 1 mL C8H18 114.2 g C8H18 2 mol C8H18 =55.3 mol CO2