Chemistry Reference
In-Depth Information
Step 2. Next, look up the masses of each element on the periodic table, and
divide the above masses by the elemental masses.
Calcium
71.5 grams/40.1 grams per part = 1.78 parts
Oxygen
28.5 grams/16.0 grams per part = 1.78 parts
Step 3. Use the number of parts to construct a simple, whole number ratio.
1.78:1.78 equals 1:1
Step 4. Use the numbers in the ratio as the subscripts in the empirical
formula.
Empirical formula
CaO
Lesson 5-4 Review
1.
Which of the following pairs could represent the molecular formula
and the empirical formula for the same compound?
a) C
3
H
8
and CH
2
c) C
4
H
8
and CH
b) C
3
H
6
and CH
2
d) C
3
H
6
and CH
3
2.
Which of the following pairs could represent the molecular formula
and the empirical formula for the same compound?
a) C
4
H
12
and CH
3
c) C
3
H
6
and CH
b) C
3
H
5
and CH
8
d) C
3
H
8
and CH
2
3.
A student determines that a compound contains 58.8% barium,
13.7% sulfur, and 27.5% oxygen by mass. Find the empirical formula
for this compound.
a) BaSO
4
b) BaSO
3
c) Ba
2
SO
d) BaS
2
O
3
4.
A laboratory experiment determines that a compound contains
57.5% sodium, 40.0% oxygen, and 2.5% hydrogen by mass. Find the
empirical formula for this compound.
a) NaOH
b) NaOH
2
c) Na
2
OH
d) Na(OH)
3
5.
A student determines that a compound contains 40.0% calcium, 12.0%
carbon, and 48.0% oxygen by mass. Find the empirical formula.
a) CaCO
4
b) CaCO
3
c) Ca
2
CO
d) CaC
2
O
3
6.
Determine the molecular formula of a compound with an empirical
formula of CH
4
and a molecular mass of 16 u (atomic mass units).
a) CH
4
b) C
2
H
8
c) CH
6
d) C
5
H
11
