# Stoichiometry

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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
• 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
 Author: kayekitty ID: 151617 Card Set: Stoichiometry Updated: 2012-05-02 04:01:49 Tags: chemistry stoich Folders: Description: unit 4 and 5 Show Answers: