Chapter three Stoichiometry (quantitative aspects of chem. Formulas and rxns)
Stoich
the study of quantitative aspects of chem formulas and rxns
Mole (SI unit for amt) 1 mol = 6.022 x10^23 (avagondros num) mass
of 12C is 12 amu/atom or 12g/mol = atomic mass of ele in amu is
numerically the same as mass of one mol atoms in grams.
Molar mass h20= 18g/mol mass per mole of its entities
Ele
Monoatomic ele (ele that occur as individual atoms) # from PT in g/mol
Molecular ele – sum together
Cmpds – the molar mass of a cmpds the sum of the molar masses of
the atoms of the ele
Converting moles mass and # chem entities
EQN
Mass (g)= # moles x (# grams/ 1 mol)
# of moles = mass (g) x (1 mol/ # grams)
# entities = # moles x (6.022x10^23entities/1 mol)
# moles= # of entities x (1 mol/ 6.022x10^23)
Converting moles of ele (massmolenumber relationships of ele)
Btwn amt (mol) and mass (g) use Molar mass (M in g/mol)
Btwn amt (mol) and # of entities use Avo’s (entities/mol) For ele as
molecules use molecular formula to find atoms/mols
Converting Moles of Cmpd
Pic 72, 73
Mass percent from chem formula Mass% of ele X= (atoms of X in
formula x atomic mass of X (amu)/ molecular (or formula) mass of
cmpd) x 100
3.2
Empirical formulas
Divide by the smallest subscript or multiply by the smallest number
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 Fall '08
 ROBERTPARSON
 Chemistry, Atom, Mole, Stoichiometry, EQN Mass, ele Converting moles, Ele Monoatomic ele

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