Empirical and Molecular Formula Worksheet
1) A compound with an empirical formula of C
OH
and a molar mass of 176 grams per mole. What is
2
4
the molecular formula of this compound?
2) A compound with an empirical formula of C
H
O and a molar mass of 68 grams per mole. What is the
4
4
molecular formula of this compound?
3) a) What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0%
oxygen?
b) If its molar mass is 110 grams per mole, what is the molecular formula?
4) a) What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0%
oxygen?
b) If the molar mass of this compound is 73.8 grams per mole, what is the molecular formula?
c) What is the name of this compound?
Answers:
1) A compound with an empirical formula of C
OH
and a molar mass of 176 grams per
2
4
mole. What is the molecular formula of this compound?
C
OH
= 44.06 grams / mole
176/44=4 so
C
O
H
2
4
8
4
16
2) A compound with an empirical formula of C
H
O and a molar mass of 68 grams per
4
4
mole. What is the molecular formula of this compound?
C
H
O = 68.08 grams / mole
68/68=1 so
C
H
O
4
4
4
4
3) a) What’s the empirical formula of a molecule containing 65.5% carbon, 5.5%
hydrogen, and 29.0% oxygen?
b) If its molar mass is 110 grams per mole, what is the molecular formula?
a) C 65.5 ( 1mole /12.01g) = 5.454 / 1.813 = 3
H 5.5 ( 1 mole / 1.01g)
= 5.446 / 1.813 = 3 so
C
H
0 molar mass = 55.06
3
3
O 29.0 ( 1 mole / 16.00 g) = 1.813 / 1.813 = 1
b)
110 / 55.06 = 2 so C
H
0
6
6
2
4) a) What’s the empirical formula of a molecule containing 18.7% lithium, 16.3%
carbon, and 65.0% oxygen?
b) If the molar mass of this compound is 73.8 grams per mole, what is the molecular
formula?
c) What is the name of this compound?
a) Li 18.7 ( 1mole / 6.94g) = 2.695 / 1.357 = 2
C 16.3 ( 1 mole / 12.01g)
= 1.357 / 1.357 = 1 so
Li
C0
molar mass = 73.89
2
3
O 65.0 ( 1 mole / 16.00 g) = 4.063 / 1.357 = 3