1. Empirical Formulas
formaldehyde CH2O
(toxic preservative)
acetic acid C2H4O2
(vinegar)
glucose C6H12O6
(simple sugar)
all have the same basic or “empirical” formula
CH2O

2. empirical formula:
smallest whole-number ratio of the atoms in a compound.
Examples:
CH2 HO PbO2 C2H6N
Non-Examples:
C6H12 H2O2 Pb2O4 C6H18N3

3. Acetylene (C2H2) is a gas used in welder’s torches.
These two compounds of carbon both have the same empirical formula (CH) but different molecular formulas.
Styrene (C8H8) is used in making polystyrene.

4. % composition  empirical formula
From To
% composition  empirical formula
Percent to Mass
Mass to Mole
Divide by Small
Times ‘til Whole
assume 100 g
g  mol using molar mass
to get ratio of atoms
no fractions of an atom

5. What is the empirical formula of a compound that is analyzed and found to contain % N and % O?
÷ by Small
% to Mass
Mass to Mole
times ‘til whole
25.9 g N
74.1 g O
x 1 mol N
14.01 g N
x 1 mol O
16.00 g O
= 1.85 mol N
= 4.63 mol O
________
1.85
= 1 N
= 2.5 O
x 2 = 2 N
x 2 = 5 O
N2O5

6. 1,6-diaminohexane is used to make nylon
1,6-diaminohexane is used to make nylon. What is the empirical formula if it is % C, % H, and % N?
÷ by Small
% to Mass
Mass to Mole
C3H8N
62.1 g C
13.8 g H
24.1 g N
x 1 mol C
12.01 g C
x 1 mol H
1.01 g H
x 1 mol N
14.01 g N
= 5.17 mol C
= 13.7 mol H
= 1.72 mol N
________
1.72
_________
= 3 C
= 8 H
= 1 N

7. Quick Quiz!
1. An empirical formula shows the __________ of atoms in a compound.
lowest common number
highest whole number ratio
lowest whole number ratio
average ratio

8. Quick Quiz.
2. Which of the following is NOT an empirical formula?
CH3
H2N CH
C3H6