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9.1 NOTES Stoichiometry

9.1 NOTES Stoichiometry. I. What is Stoichiometry? Definition: the study of quantitative relationships between the amounts of reactants used and products formed by a chemical reaction; based on the law of conservation of mass and energy.

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9.1 NOTES Stoichiometry

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  1. 9.1 NOTESStoichiometry

  2. I. What is Stoichiometry? • Definition: the study of quantitative relationships between the amounts of reactants used and products formed by a chemical reaction; based on the law of conservation of mass and energy

  3. Mole and mass relationships in chemical reactions • balanced chemical equation gives the mole ratio coefficients represent not only individual particles, but also number of moles; mole ratio – ratio between the # of moles of any 2 substances • # species in eqn. x next lower # = # of mole ratios (n x (n-1)) = # mole ratios;

  4. i.e. Iron + Oxygen  Iron (III) oxide = • 4Fe + 3O2 2Fe2O3 = • 4 atoms of Fe + 3 molecules O2 2 formulaunits Fe2O3 • 4 moles Fe + 3 mole O2  2 moles Fe2O3 = 223.4g Fe + 96.0g O2 319.4g Fe2O3

  5. II. Stoichiometric Calculations • A. Mass-mass calculations • Example: What mass of hydrogen gas can be formed when 12.5 grams of zinc reacts with excess hydrochloric acid? • How to approach a stoichiometry problem: • 1. Read the problem, then write a balanced equation. • 2. Identify the given and desired quantities. • 3. Determine molar masses if necessary. • 4. Carry out the factor-label calculation, labeling the answer with units.

  6. a. Do the above example: • Zn + 2HCl  ZnCl2 + H2 • Given: 12.5 grams of Zn (65.4g/mol) Find: mass of H2 (2.02g/mol) • 12.5gZn x 1 mol Zn x 1 mol H2x2.02 g H2 • 65.4 g Zn 1 mol Zn 1 mol H2 = 0.386 g H2

  7. b. When 10.0 grams of propane (C3H8) is burned in air, what is the mass of water formed? • C3H8 + 5O23CO2+ 4H2O • Given: 10.0g C3H8 *44.1g/mol) Find: mass of H2O (18.0g/mol) • 10.0gC3H8 x 1 mol C3H8 x 4 mol H2O x 18.0g H2O • 44.1 g C3H8 1 mol C3H8 1 mol H2O = 16.3g H2O

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