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Stoichiometry

Stoichiometry. What It Is And Why We Need It. Stoichiometry. Pronounced stoi-kee-om-i-tree Derived from the Greek words stoicheion, meaning element and metron, meaning measure. Stoichiometry.

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Stoichiometry

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  1. Stoichiometry What It Is And Why We Need It

  2. Stoichiometry • Pronounced stoi-kee-om-i-tree • Derived from the Greek words stoicheion, meaning element and metron, meaning measure.

  3. Stoichiometry • Stoichiometry is based on the law of conservation of mass, which was introduced by Antoine Lavoisier in the eighteenth century.

  4. Law of Conservation of Mass • The law states that matter is neither created nor destroyed in a chemical reaction. • Chemical bonds in reactants break and new chemical bonds form to produce products. • The amount of matter present at the end of a reaction is the same present at the beginning of the reaction.

  5. Stoichiometry and the Balanced Chemical Equation 4Fe(s) + 3O2(g)  2Fe2O3(s) • Different interpretations of the equation: • Atoms and molecules 4 atoms Fe + 3 molecules O2 2 molecules Fe2O3 • Since 6.02 x 1023 atoms are related to 1 mole 4 mol Fe + 3 molO2 2 mol Fe2O3 • Note that the chemical equation does not say anything about masses

  6. Stoichiometry and the Balanced Chemical Equation 4Fe(s) + 3O2(g)  2Fe2O3(s) 4 mol Fe + 3 mol O2 2 mol Fe2O3 • Mass is related to moles according to the periodic table. • 1 mol Fe = 55.85 g Fe • 1 mol O2 = 32.00 g O2 • 1 mol Fe2O3 = 159.7 g Fe2O3

  7. Stoichiometry and the Balanced Chemical Equation 4Fe(s) + 3O2(g)  2Fe2O3(s) 223.4 g Fe + 96.00 g O2 319.4 g Fe2O3 319.4 g reactants  319.4 g products

  8. Interpreting Chemical Equations C3H8(g) + 5O2(g)  3CO2(g) + 4 H2O(g) • The equation in terms of molecules: 1 molecule C3H8 + 5 molecule O2 3 molecule CO2 + 4 molecule H2O • The equation in terms of moles: 1 mol C3H8 + 5 mol O2 3 mol CO2 + 4 mol H2O • The equation in terms of mass: 44.09 g C3H8 + 160.0 g O2 132.0 g CO2 + 72.07 g H2O Double check Law of Conservation of Masses 204.1 g reactants = 204.1 g products

  9. Mole Ratios • A ratio between the numbers of moles of any two substances in a balanced Chemical Equation. 2Al(s) + 3 Br2(g)  2 AlBr3(s) 2 mol Al : 3 mol Br2 : 2 mol AlBr3

  10. Mole Ratios 2 mol Al : 3 mol Br2 : 2 mol AlBr3

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