unit 3 Flashcards
the mole
N= n x NA
n= N/NA
n is moles
N is particles
NA is avogardo’s constant
how do you find atoms?
number of molecules x number of atoms in formula
solving for mass
m= n x MM
m is mass in grams
n is number of moles
MM is molar mass in g/mol
percent composition
%composition = mass of element in compound/ total mass of compound (100)
empirical formula
1) assume a 100g same size and convert % to grams
2) convert mass to moles
3) find ratio by dividing by smallest number of moles
4) state formula
molecular formula
-calculate molar mass of EF
-determine ratio —> ratio= MMMF/MMEF
MF= EF x ratio
how do you find empirical formula from the molecular formula
reduce MF to simplest terms
stoichiometry
-make sure equation is balanced
-n find = n given x coefficient find/ coeffient given
limiting and excess reagents
-balance equation
-use masses calculate moles of each
-LF or ER = moles/coeffient
smaller value is limiting
what is theoretical yield
amount that should be produced, found using stoichometry
what is actual yield
actual amount produced
how do you find percent yield
PY = AY/TY x100
why is percent yield not always 100%
-human error
-instruament inaccuracy
-stirring rod
-heating/ not heating reactant to high remp
