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Stoichiometry

Stoichiometry. Chem 332 – O’Dette. Why care about stoichiometry?. Stoichiometry: allows us to predict the amounts of product produced or reactant needed in a reaction. Problem Types. Mole to Mole (one step) Mole to Mass (two steps) Mass to Moles (two steps) Mass to Mass (three steps).

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Stoichiometry

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  1. Stoichiometry Chem 332 – O’Dette

  2. Why care about stoichiometry? • Stoichiometry: allows us to predict the amounts of product produced or reactant needed in a reaction

  3. Problem Types • Mole to Mole (one step) • Mole to Mass (two steps) • Mass to Moles (two steps) • Mass to Mass (three steps)

  4. Mole Ratio • A conversion factor that relates the amounts in moles of any two substances in a reaction • Use the coefficients in a balanced equation

  5. Mole to Mole • 2 Al2O3 4 Al + 3 O2 • Mole Ratios • 2 moles Al2O3 : 4 moles Al • 2 moles Al2O3 : 3 moles O2 • 4 moles Al : 3 moles O2

  6. Mole Ratio Conversion Factors • 2 moles Al2O3 4 moles Al • 2 moles Al2O3 3 moles O2 • 4 moles Al 3 moles O2 • Remember Reciprocals!!!

  7. Example #1 • If we have 12 moles of Al2O3, how many moles of Al and O2 are produced? • 12 moles Al2O3 x • 12 moles Al2O3 x 4 moles Al = 24 moles Al moles Al2O3 2 3 moles O2 18 moles O2 = 2 moles Al2O3

  8. Mole to Mass • Example #2 : How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? • 2 Na + Cl2 2 NaCl

  9. Example #2 (continued) 70.90 g Cl2 1 mole Cl2 • 5 moles Na x x 1 mole Cl2 2 mole Na Mole Ratio MM Use the mole ratio to convert to the substance asked for = 177 grams Cl2

  10. Example #3 • Calculate the mass of iodine required to react completely with 0.50 mole of aluminum to produce aluminum iodide. • 3 I2 + 2 Al 2AlI3

  11. Example #3 (continued) 253.8 g I2 3 mole I2 • .5 moles Al x x 1 mole I2 2 mole Al = 190 grams I2

  12. Mass to Mole • Example #4 : Calculate how many moles of zinc are required to make 10.0 g of zinc chloride. • Zn + Cl2 ZnCl2

  13. Example #4 (continued) 1 mole ZnCl2 1 moles Zn • 10 g ZnCl2 x x 1 mole ZnCl2 136.29 g ZnCl2 MM Mole Ratio = 0.0734 mole Zn

  14. Example #5 • Calculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water in a combustion reaction. • 2 C2H6 + 7 O2 6 H2O + 4 CO2

  15. Example #5 (continued) 1 mole H2O 2 moles C2H6 • 10 g H2O x x 6 moles H2O 18.02 g H2O = 0.185 moles C2H6

  16. Mass to Mass • Mass Moles Moles Mass • These will be the steps every time!! Molar Mass Mole Ratio Molar Mass

  17. Example #6 • Tin(II) fluoride, SnF2, is used in some toothpastes it is made by the reaction of tin with hydrogen fluoride according to the following equation. • Sn + 2 HF SnF2 + H2

  18. Example #6 (continued) • How many grams of SnF2 are produced from the reaction of 30.00 g HF with Sn? • 30 g HF x xx 1 mole HF 1 mole SnF2 159.69 g SnF2 20.00 g HF 2 moles HF 1 mole SnF2 = 117.5 g SnF2

  19. Example #7 • When copper metal is added to silver nitrate in solution, silver metal and copper(II) nitrate are produced. What mass of silver is produced from 100 g of Cu? • Cu + 2 AgNO3 2 Ag + Cu(NO3)2

  20. Example #7 (continued) • 100 g Cu x xx 107.87 g Ag 1 mole Cu 2 moles Ag 1 mole Ag 1 mole Cu 63.55 g Cu = 300 g Ag

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