Download Empirical Formulas: Formulas in the lowest whole number

Empirical Formulas: Formulas in the lowest whole
number ratio. Ex: NaCl MgCl2 H2O
Molecular Formulas: Formulas that show the exact
number of atoms of each element in a compound.
Ex: C6H12O6 N2O4 H2O ** A compound can
have the same EF and MF.
Calculations Yeah!!!!!! Wooo-hoooo
How to calculate an Ef from % comp or mass of the
parts.
** If given % by mass the percents of each element
are their masses in grams.
Steps for calculating EF
1. Mass to moles (for each element)
2. divide by small (divide each number of moles by
the smallest number of moles of all the elements in
the compound.)
3. Multiply till whole. (if you get a fractional answer
for one or more of the answers above. You need to
multiply all the answers by whatever whole number
you need to make them all whole numbers.)
Example Question 11 on 10-3 R&R Worksheet
How do you calculate a MF? You need 2 pieces of
information.
1. You need the EF (or the info to calculate it)
2. You need the Molar Mass (GFM).
Steps
1. Calculate the GFM of the EF (EF mass)
2. Divide the Molar mass by the EF mass to get
whole number multiple.
3. Multiply the coefficients of the EF by the whole
number multiple to get MF.
Ex. #13.