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Stoichiometry

Stoichiometry. October 11, 2011. Stoichiometry. Stoichiometry: math of chemical reactions Balanced equations tell us a lot of information. Balanced Chemical Equations. Practice. Hydrogen sulfide is found in volcanic areas. The balanced equation is

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Stoichiometry

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  1. Stoichiometry October 11, 2011

  2. Stoichiometry • Stoichiometry: math of chemical reactions • Balanced equations tell us a lot of information

  3. Balanced Chemical Equations

  4. Practice • Hydrogen sulfide is found in volcanic areas. The balanced equation is 2H2S (g) + 3O2(g) 2SO2 (g) + 2H2O (g) • Find the number of representative particles • 2 molecules H2S + 3 molecules O2 2 molecules SO2 + 2 molecules H2O

  5. Practice • Hydrogen sulfide is found in volcanic areas. The balanced equation is 2H2S (g) + 3O2(g) 2SO2 (g) + 2H2O (g) • Find the number of moles • 2 moles H2S + 3 moles O2 2 moles SO2 + 2 moles H2O

  6. Practice • Hydrogen sulfide is found in volcanic areas. The balanced equation is 2H2S (g) + 3O2(g) 2SO2 (g) + 2H2O (g) • Find the masses of the reactants and products • Use the atomic masses on the periodic table! • 2(2x1 + 32)g+ 3 (2x16)g  2(32 + 2x16)g+ 2(2x1 + 16)g 2(34)g + 3(32)g  2(64)g + 2(18)g 128g  128g

  7. Mole  Mole conversions N2 + 3H2 2NH3 Mole ratios… 1 mole N2 3 moles H2 1 mole N2 3 moles H2 1 moles N2 2 moles NH3 2 moles NH3 3 moles H22 moles NH3 3 moles H2 2 moles NH3 3 moles H2

  8. Mole  Mole conversions N2 + 3H2 2NH3 • How many moles of ammonia are produced when 0.5 moles of nitrogen react with hydrogen? • How many moles of nitrogen will react with 7.0 moles of hydrogen gas?

  9. Mass  Mass conversions N2 + 3H2 2NH3 • If 56 g N2 reacts with excess hydrogen, how much ammonia is produced? • excess = extra

  10. Mass  Mass conversions N2 + 3H2 2NH3 • If 56 g N2 reacts with excess hydrogen, how much ammonia is produced?

  11. Stoichiometric Map

  12. Volume-volume • Assuming STP, how many liters of oxygen are required to produce 19.8 L SO3? 2SO2 + O2 2SO3

  13. Mass to volume • Assuming STP, how many liters of SO3 can be produced when 48 grams O2 react with excess SO2? 2SO2 + O2 2SO3

  14. Particles to Mass • Tin (II) fluoride used to be a common ingredient in toothpaste. It is formed with this reaction: Sn + HF  SnF2 + H2 • Balance the equation Sn + 2HF  SnF2 + H2 • How many grams of SnF2 can be produced by reacting 7.22 x 1023 molecules of HF with excess tin?

  15. Why? • Why do we balance equations? • Law of Conservation of Matter • What is conserved during a reaction? • Atoms • Mass • NOT necessarily moles • We can use the balanced equation to determine limiting reagent

  16. Limiting reagent • How many complete cars can be produced from eight car bodies and 48 tires? • How many complete cars can be produced from 12 car bodies and 36 tires? What is the limiting reagent? What is in excess? • 36 tires/4 tires per car = 9 complete cars • Tires are the limiting reagent; car bodies are excess

  17. Limiting reagent 2Cu + S(s)  Cu2S What is the limiting reagent when 80.0 grams copper react with 25.0 grams sulfur? What is the maximum number of grams of Cu2S that can be formed?

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