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2012-05-02 00:01:49
chemistry stoich

unit 4 and 5
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  1. law of definite proportions
    specific compound always contains same elements in definite proportions by mass
  2. relative atomic mass
    • u <-- unit
    • mass of an element tt would react w/ fixed mass of standard element
    • c-12, 1/12 mass the mass of a carbon 12 isotope as one unified atomic mass unit
    • measured mass of all other atoms relative to this
  3. isotopic abundance
    % of an isotope in a sample of element
  4. avaerage atomic mass
    sum of (% abundance of isotope x mass isotope)
  5. mole
    grouping used for molecules/atoms so tt we can deal w/ them easier
  6. avagadro's constant
    • amount we group atoms in
    • 6.02x10^23
  7. molar mass
    • mass in g/mol o one mole o substance
    • atomic mass of periodic table
  8. mass percent
    mass o element in compound, expressed as percent o total mass o compound
  9. percentage composition
    relative mass o each element in compound
  10. empirical formula
    lowest whole #ratio o elements in compound , simplest ratio
  11. molecular formula
    shows number o atoms o each element tt make up molecule or formula
  12. stoichiometry
    study o relative quantities o reactants and products in chemical reaction
  13. mole ratio
    • relationship between moles in a balanced chemical equation
    • can only compare in molc or moles
  14. limiting reagent
    reactant completed consumed in chemical reaction
  15. excess reagent
    reactant tt is present in more than required amount for complete reaction
  16. an excess of how much should be used to ensure limiting reagent is completely used?
    10% of mol
  17. when determining limiting reagent, what must you always do?
    always multiply moles out to find the moles of product for each reactant
  18. yield
    amount of product obtained in chemical reaction
  19. theoretical yield
    amount o product that we predict will be obtained
  20. actual yield
    amount o product that is actually obtained at end o experiment
  21. reasons why reactions don't yield 100%?
    • SIN
    • side reactions
    • impurities in reagents
    • not ideal conditions for reaction
    • experimental procedures