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Stoichiometry: Calculations and Conversions

This chapter covers the principles of stoichiometry, including ideal stoichiometric calculations, stoichiometric conversions, limiting reactant problems, and percent yield.

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Stoichiometry: Calculations and Conversions

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  1. Chapter 9 Stoichiometry

  2. 9.1 & 9.2 Ideal Stoichiometric Calculations • Stoichiometry - the study of the quantitative measurement problems between chemical formulas, reactions and equations.

  3. Liters 22.4 L Mole Molar Mass 6.022 x1023 Atoms, molecules, particles Grams The Mole Map

  4. Stoichiometric Conversions • Quick Review using the mole map • Ex1: • 0.15 mol NaOH convert to grams • Ex2: • 9.00g MgCl2 convert to atoms of Chlorine

  5. Stoichiometric Conversions • Reaction stoichiometry • Example - combustion of propane: • C3H8 + __O2__CO2 + __H2O • Thus, for every 1 propane, 5 moles of diatomic oxygen are required to produce 3 moles of carbon dioxide and 4 moles of water.

  6. Liters Liters Coefficients Mole Mole Grams Molecules Grams The New Mole Map Molecules

  7. Stoichiometric Conversions • Four Core Steps: • Step #1 Write a BALANCED equation • Step #2 Go to moles • Step #3 Mole to Mole - cross the bridge • Step #4Go to the desired unit

  8. Stoichiometric Conversions • Ex1: How many moles of water vapor are created from 2 moles of Hydrogen? • Balanced equation • Go to Mole • Mole to Mole • Desired Unit

  9. Stoichiometric Conversions • Ex2: How many grams of water vapor are created from 64.0 grams of Oxygen? • Balanced equation • 2H2(g) + O2(g) 2H2O(g) • Go to Mole • Mole to Mole • Desired Unit

  10. Stoichiometric Conversions • Ex3: How many liters of H2O (g) are made from 5.00 L of Oxygen? • Balanced equation • 2H2(g) + O2(g) 2H2O(g) • Go to Mole • Mole to Mole • Desired Unit

  11. Stoichiometric Conversions • Ex4: How many Liters of Oxygen are needed to react with 14.40 g C5H12? • Balanced equation • Go to Mole • Mole to Mole • Desired Unit

  12. Stoichiometric Conversions • Ex5: How many grams of solid lithium hydroxide are needed to react with 8.50 grams of carbon dioxide gas? • (Lithium hydroxide + carbon dioxide yields Lithium carbonate and water) 9.23g LiOH

  13. Stoichiometric Conversions • Ex6: How many grams of water are produced from 2.00 moles of carbon dioxide and excess amount of lithium hydroxide? 36.0g • Ex7: How many moles of lithium carbonate are produced from 152 grams of carbon dioxide and an excess amount of lithium hydroxide? 3.45mol

  14. 9.3 Limiting Reactant Problems and % Yield... • The Limiting Reactant causes the reaction to stop…it is the reactant that is all used up in the chemical reaction.

  15. Limiting Reactant • Ex1: How many grams of Magnesium Chloride can be made from 3.64 g of magnesium and 7.10 g of Chlorine gas? • a: How much of the excess reactant did you use? • b: What percent of the excess was unused? ……

  16. Limiting Reactant • How many grams of Magnesium Chloride can be made from 3.64 g of magnesium and 7.10 g of Chlorine gas?

  17. Limiting Reactant • How much of the excess reactant did you use?

  18. Limiting Reactant • What percent of the excess was unused?

  19. Limiting Reactant and % Yield • .From the equation: 2 HCl + Zn  ZnCl2 + H2 • How many liters of H2 can be made starting with 20.0 grams of Zn and 25.5 g HCl? • How many grams of Zinc chloride will be made? • Identify the limiting and excess reactants. • How much of the excess reactant is needed? • How much of the excess reactant is left over?

  20. Limiting Reactant • 2 HCl + Zn  ZnCl2 + H2 • How many liters of H2 can be made starting with 20.0 grams of Zn and 25.5 g HCl?

  21. Limiting Reactant • 2 HCl + Zn  ZnCl2 + H2 • How many grams of Zinc chloride will be made?

  22. Limiting Reactant • 2 HCl + Zn  ZnCl2 + H2

  23. Limiting Reactant • Identify the limiting and excess reactants. • How much of the excess reactant is needed? • How much of the excess reactant is left over?

  24. % Yield • % yield = mass produced x 100 mass theoretically produced

  25. % Yield • Ex1: If combusting 9.62 g of SO2 produces 11.95 g of SO3, calculate the % yield.

  26. % Yield • Ex2: Reacting 4.20 grams of Nitrogen with 0.800 g of Hydrogen produces ?g of NH3 if there is a 75.5 % yield? Thus, the limiting reactant, H2, theoretically produces _________ grams of NH3. So, if the % yield is ________, then the actual yield is:

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