Section 11.4
Empirical and Molecular Formulas
Practice Test
1.
Analysis of a covalent compound showed that it contained 14.4% hydrogen and 85.6% carbon by mass. What is the empirical formula for this compound?
SC.A.1.4.5
a.
CH
b.
C
2
H
3
c.
CH
2
d.
CH
3
Hint
2.
What mass of iron is contained in 62.8 grams of pyrite FeS
2
?
a.
31.7 g
b.
58.5 g
c.
29.2 g
d.
40.3 g
Hint
3.
How can the actual molecular formula be determined?
a.
from the molar mass divided by the mass of the empirical formula
b.
from the molar mass alone
c.
from the empirical formula alone
d.
from the molar mass multiplied by the mass of the empirical formula
Hint
4.
What relationship is described by the formula below?
mass of the element/mass of the compound
x 100
a.
Avogadro’s number
b.
percent composition
c.
empirical formula
d.
mole ratio
Hint
5.
An empirical formula mass is found to be 17 g/mol. The molar mass is found to be 34 g/mol. What is the number of empirical formula units in this molar mass?
a.
0.5 unit
b.
17 units
c.
1 unit
d.
2 units
Hint
6.
A compound contains sulfur, oxygen, and chlorine. Analysis of a sample showed that it contained by mass 26.95% sulfur and 59.61% chlorine. What is the simplest formula for this compound?
SC.A.2.4.2
a.
SOCl
2
b.
SOCl
c.
SO
2
Cl
2
d.
SO
2
Cl
Hint
7.
A 4.628-g sample of an iron oxide was found to contain 3.348 g of iron and 1.280 g of oxygen. What is the simplest formula for this compound?
SC.A.2.4.2
a.
FeO
2
b.
Fe
3
O
4
c.
FeO
d.
Fe
2
O
3
Hint
8.
What is the percent composition of carbon dioxide CO
2
?
a.
33% C and 66% O
b.
27% C and 73% O
c.
50% C and 50% O
d.
73% C and 27% O
Hint
9.
What mass of calcium metal could be obtained from 1 kg of limestone that is 50.0% pure CaCO
3
?
a.
0.2 kg
b.
0.4 kg
c.
0.05 kg
d.
0.5 kg
Hint
