Moles Flashcards
Avogrado’s number
Number of particles found in one mole of a substance
Molar mass
The mass of one mole of a substance, usually expressed in grams or kilograms
Percent composition
The percentage by mass of each element in a compound
Empirical formula
Formula that shows the ratio of elements present in the compound. Ratios are denoted by subscripts next to the element symbol
Molecular formula
Expression that states the number and type of atoms present in a molecule of a substance
step one for conversions?
known over 1
how do I calculate percent composition?
% mass = grams of element
___________________ x 100
total grams of compound
how do I find molar mass?
you look at a periodic table and look at the mass of the element ( if there is a coefficient that’s is bigger than 1 you multiply the mass times the coefficient. you do the same for the rest of the elements and add it all up. your total is your molar mass.
how do I calculate the empirical formula?
- ) pretend you have 100 gram sample of the compound (just change the % to grams)
- ) convert the grams to moles for each element
- ) divide each # of moles by the same smallest #
- ) IF NEEDED, multiply the result to get whole numbers. NO DECIMALS!!
how do I calculate molecular formula?
take or solve for empirical formula
solve molar mass of molecular formula and empirical formula.
divide molecular formula molar mass by empirical formula’s molar mass.
moles road map
Volume
22.4L
\_\_\_\_\_
Mole↓
↓
Mole
↙ ↘
Mass representative particles
G/moles 6.02x10^23 RP
Rp= atoms/molecules/formula/grams to grams
grams x moles x moles x grams
known over 1 x
1 mole of known compound over molar mass of known compound x
moles of unknown compound over moles of known compound x
mass of unknown compound over 1 mole of unkown compund
limiting reactant
TWO grams to grams to grams.
which one will be your limiting reactant?
smallest product
percent yield formula
Actual yield
___________ x 100%
theoretical yield
what do you have to calculate in order to get the
TY ( theoretical yield)
grams to gram equation for limiting reactant
how do you calculate the excess left over in a limiting reactant reaction?
subtract what you get as the smallest number after limiting reactant grams to grams equation from known \_\_\_\_\_ 1 that was not used.
process in converting moles to grams
put known over 1
multiply
by molar mass over one
moles cross out so answer should be in grams
process in converting moles to moles
MAKE SURE EQUATION IN BALANCED
known over one
multiply times
moles of unknown over moles of known
Mole
Chemical mass unit 6.022 • 10^23 molecule/atoms/or other unit
