Stoichiometry

• What is the Law of Definite Proportions also known as?


  Proust’s Law
• What does the Law of Definite Proportions state?


  A given chemical compound always contains the same elements in the exact same proportions by mass.
• If a sample of pure water contains 11.19% hydrogen by mass, what is the percentage of oxygen by mass?


  88.81%
• What is the Law of Multiple Proportions also known as?


  Dalton’s Law
• What does the Law of Multiple Proportions state?


  When one element combines with another to form more than one compound, the mass ratios of the elements in the compounds are simple whole numbers.
• What is the mass ratio of oxygen when 100g of carbon combines to form CO and CO₂?


  266:133 = 2:1
• What does stoichiometry involve?


  • Measuring amounts of elements and compounds in reactions
  • Using chemical equations to show relationships between reactants and products
• What does the term "stoichio" mean in Greek?


  Element
• What is the balanced chemical equation for the reaction involving ammonia and oxygen?


  4NH₃ + 5O₂ → 6H₂O + 4NO
• What does the equation 4NH₃ + 5O₂ → 6H₂O + 4NO indicate about the reactants and products?


  4 moles of NH₃ react with 5 moles of O₂ to produce 6 moles of H₂O and 4 moles of NO.
• What do the coefficients in a balanced chemical equation represent?


  • The mole ratio of the substances involved in the reaction
  • Example: In 4NH₃ + 5O₂ → 6H₂O + 4NO, the mole ratio is 4:5:6:4
• How do you calculate molar masses?


  By adding the atomic masses of the elements.
• What are the steps for converting between substances in stoichiometry?


  1. Grams (x) → Moles (x) → Moles (y) → Grams (y)
  2. Use molar mass and mole ratio as key conversion factors
• Why can't you directly convert from grams of one compound to grams of another?


  You must first convert grams to moles, use the mole ratio, then convert back to grams.