Chemical Formulas and
Chemical Compounds
Chapter 7 Review – Answers
Pages 53 - 54
1.
2.
C. The charge on each Fe
In a stock name
ion
such as iron(III)
sulfate, the roman
number tells us
____.
The result of
C. Change the formula so
changing a
that it no longer
subscript in a
represents the
correctly written
compound it previously
chemical formula
represented.
is to _____.
Pages 53 - 54
3.
The explosive TNT has the molecular
formula C7H5(NO2)3.
a. How many elements make up this compound?
4 elements
b. How many oxygen atoms are present in one
molecule of C7H5(NO2)3?
6 oxygen atoms
c. How many atoms in total are present in one
molecule of C7H5(NO2)3?
21 atoms
d. How many atoms are present in a sample of 2 
1023 molecules of C7H5(NO2)3?
atoms
2 10 molecules  21
 4.2 10 24 atoms
molecule
23
Pages 53 - 54
4.
How many atoms are present in
each of these formula units?
a. Ca(HCO3)2 11 atoms
b. C12H22O11 45 atoms
c. Fe(ClO2)3 10 atoms
d. Fe(ClO3)2 9 atoms
Pages 53 - 54
5.
(see below)
a. What is the formula for the compound
dinitrogen pentoxide?
N2O5
b. What is the Stock name for the
covalent compound CS2?
Carbon disulfide
Pages 53 - 54
6.
Some binary compounds are ionic,
others are covalent. The types of
bonding partially depend on the
position of the elements in the
periodic table. Label each of these
claims as True or False; if False,
specify the nature of the error.
a. Covalently bonded binary molecular
compounds typically form from
nonmetals.
True
Pages 53 - 54
6.
Some binary compounds are ionic,
others are covalent. The types of
bonding partially depend on the
position of the elements in the
periodic table. Label each of these
claims as True or False; if False,
specify the nature of the error.
b. Binary ionic compound form from
metals and nonmetals, typically from
opposite sides of the periodic table.
True
Pages 53 - 54
6.
Some binary compounds are ionic,
others are covalent. The types of
bonding partially depend on the
position of the elements in the
periodic table. Label each of these
claims as True or False; if False,
specify the nature of the error.
c. Binary compound involving metalloids
are always ionic.
False; metalloids on the right of the stair-step
line act as nonmetals in compounds
Pages 53 - 54
8.
Fill in the blanks in the table below.
Compound Name
Formula
Aluminum sulfide
Al2S3
Aluminum sulfite
Al2(SO3)3
Lead(II) chloride PbCl2
Ammonium phosphate (NH4)3PO4
Pages 55 - 56
4.
Tin has possible oxidation numbers
of +2 and +4 and forms two known
oxides. One of them has the
formula SnO2.
a. Give the stock name for SnO2.
Tin(IV) oxide
b. Give the empirical formula for the
other oxide of tin.
SnO
Pages 55 - 56
5.
Scientists believe that two separate reactions
contribute to the depletion of the ozone layer, O3.
The first reaction involves oxides of nitrogen. The
second involves free chlorine atoms. Both reactions
follow. When a compound is not stated as a
formula, write the correct formula in the blank
beside its name.
a. _____(nitrogen
monoxide) + O3 →
NO
NO2 (nitrogen dioxide) + O2
______
b. Cl + O3 → ______
ClO (chlorine monoxide) + O2
Pages 55 - 56
6.
Consider the covalent dinitrogen
trioxide when answering the
following:
a. What is the formula for dinitrogen
trioxide? N2O3
Pages 57 - 58
1.
Label each of the following statements as
True or False:
True a.
If the formula mass of one molecule is x
amu, the molar mass is x g/mol.
False b.
Samples of two different chemicals with
equal numbers of moles must have equal
masses as well.
True c.
Samples of two different chemicals with
equal numbers of moles must have equal
numbers of molecules as well.
Pages 57 - 58
2.
How many moles of each element
are present in a 10.0 mol sample of
Ca(NO3)2?
10.0 mol calcium
20.0 mol nitrogen
60.0 mol oxygen
Pages 57 - 58
3.
Consider a sample of 10.0 g of the gaseous
hydrocarbon C3H4 to answer the following
questions.
a. How many moles are present in this sample?
10.0 g
mol

 0.25 mol
40.0 g
b. How many molecules are present in the C3H4
sample?
0.25 mol
6.02 10 molecules
23

 1.50 10 molecules
mol
23
Pages 57 - 58
3.
Consider a sample of 10.0 g of the gaseous
hydrocarbon C3H4 to answer the following
questions.
c. How many carbon atoms are present in this
sample?
1.50 1023 molecules
3 carbon atoms
23

 4.50 10 atoms
molecule
d. What is the percentage composition of hydrogen
in the sample?
g
4.0
H
mol
100  10.0%H
g
40.0
C3 H 4
mol
Pages 57 - 58
4.
The chief source of aluminum metal is the
ore alumina, Al2O3.
a. Determine the percentage composition of Al in
this ore.
g
54
Al
mol
100  52.9% Al
g
102
Al 2 O3
mol
b. How many pounds of aluminum can be
extracted from 2.0 tons of alumina?
4000 lbs ore 0.529 lb Al

 2100 lb Al
1 lb ore
Pages 57 - 58
5.
Compound A has a molar mass of 20 g/mol, and
compound B has a molar mass of 30 g/mol.
a. What is the mass of 1.0 mol of compound A?
20 grams
b. How many moles are present in 5.0 g of
compound B?
5.0 g
mol

 0.17 mol
30.0 g
c. How many moles of compound B are needed to
have the same mass as 6.0 mol of compound A?
6.0 mol A 20 g A

 120 g A
mol A
120 g B mol B

 4 mol B
30 g B
Pages 59 - 60
1.
Write empirical formulas to match
the following molecular formulas:
a. C2H6O4 CH O
3 2
b. N2O5 N O
2 5
c. Hg2Cl2 HgCl
d. C6H12 CH2
Pages 59 - 60
2.
A certain
hydrocarbon has an
empirical formula of
CH2 and a molar
mass of 56.12
g/mol. What is its
molecular formula?
12.0
g
g
g
 2 1.0
 14.0
mol
mol
mol
g
56.12
mol  4
g
14.0
mol
C4H8
Pages 59 - 60
3.
A certain ionic
compound is found
to contain 0.012 mol
of sodium, 0.012
mol of sulfur, and
0.018 mol of
oxygen.
0.012 mol Na
 1 2  2
0.012
0.012 mol S
 1 2  2
0.012
0.018 mol O
 1.5  2  3
0.012
a. What is its empirical
Na2S2O3
formula?
b. Is this compound a
sulfate, sulfite, or
neither
neither?
Pages 59 - 60
5.
Gas X is found to be 24.0% carbon and
76.0% fluorine by mass.
a. Determine the empirical formula of gas X.
24.0 g C 2 mol C

1
g
2
12.0
mol
76.0 g F 4 mol F

2
g
2
19.0
mol
CF2
Pages 59 - 60
5.
Gas X is found to be 24.0% carbon and
76.0% fluorine by mass.
b. Given that the molar mass of gas X is 200.04
g/mol, determine its molecular formula.
g
g 
g

12.0
 2  19.0
  50
mol
mol 
mol

g
200
mol  4
g
50
mol
C4F8
Pages 59 - 60
6.
A compound is found to contain 43.2%
copper, 24.1% chlorine and 32.7% oxygen
by mass.
a. Determine its empirical formula.
43.2 g Cu 0.6803 mol Cu

1
g
0.6803
63.5
mol
24.1 g Cl 0.6808 mol Cl

1
g
0.6803
35.4
mol
32.7 g O 2.043 mol O

3
g
0.6803
16.0
mol
CuClO3
Pages 59 - 60
6.
A compound is found to contain 43.2%
copper, 24.1% chlorine and 32.7% oxygen
by mass.
b. What is the correct Stock name of the
compound in part a?
Copper(I) chlorate
Pages 61 - 64
1.
Write formulas for the following
compounds:
a. Copper(II) carbonate CuCO3
b. Sodium sulfite Na2SO3
c. Ammonium phosphate (NH4)3PO4
d. Tin(IV) sulfide SnS2
Pages 61 - 64
2.
Write the Stock names for the
following compounds:
a. Mg(ClO4)2 Magnesium perchlorate
b. Fe(NO3)2 Iron(II) nitrate
c. Fe(NO2)3 Iron(III) nitrite
d. CoO Cobalt(II) oxide
Pages 61 - 64
3.
(see below)
a. How many atoms are representd by
the formula Ca(HSO4)2?
13
b. How many moles of oxygen atoms are
in a 0.50 mol sample of this
compound? 4 mol oxygen
Pages 61 - 64
5.
Following are samples of four
different compounds. Arrange
them in order of increasing mass,
from smallest to largest.
a. 25 g of oxygen gas
b. 1.00 mol of H2O
c. 3  1023 molecules of C2H6
d. 2  1023 molecules of C2H6O2
c, b, d, a
Pages 61 - 64
6.
(see below)
a. What is the formula for sodium
hydroxide? NaOH
b. What is the formula mass of sodium
hydroxide? 40 g/mol
c. What is the mass in grams of 0.25 mol
of sodium hydroxide?
10 grams
Pages 61 - 64
7.
8.
What is the percentage composition
of ethane gas, C2H6, to the nearest
whole number?
80% carbon, 20% hydrogen
Ribose is an important sugar (part
of RNA), with a molar mass of
150.15 g/mol. If its empirical
formula is CH2O, what is its
molecular formula?
C5H10O5
Pages 61 - 64
9.
Butane gas, C4H10, is often used as
a fuel.
a. What is the mass in grams of 3.00 mol
of butane? 174 grams
b. How many molecules are present in
that 3.00 mol sample?
1.81  1024 molecules
c. What is the empirical formula of the
gas? C H
2 5
Pages 61 - 64
10.
Napthalene is a soft covalent solid
that is often used in mothballs. Its
molar mass is 128.18 g/mol and it
contains 93.75 % carbon and 6.25
% hydrogen. Determine the
molecular formula of napthalene
from this data.
C10H8
Pages 61 - 64
11.
Nicotine has the formula CxHyNz. To determine
its composition, a sample is burned in excess
oxygen, producing the following results:
1.0 mol of CO2
0.70 mol of H2O
0.20 mol of NO2
Assume that all the atoms in nicotine are
present as products.
a.
Determine the number of moles of carbon present in
the products of this combustion. 1.0 mol C
b.
Determine the number of moles of hydrogen present
in the products of this combustion.
1.4 mol H
c.
Determine the number of moles of nitrogen present in
the products of this combustion.
0.2 mol N
Pages 61 - 64
11.
Nicotine has the formula CxHyNz. To determine
its composition, a sample is burned in excess
oxygen, producing the following results:
1.0 mol of CO2
0.70 mol of H2O
0.20 mol of NO2
Assume that all the atoms in nicotine are
present as products.
d.
Determine the empirical formula of nicotine based on
your calculations.
e.
In a separate experiment, the molar mass of nicotine
is found to be somewhere between 150 and 180
g/mol. Calculate the molar mass of nicotine to the
nearest gram.
C5H7N
162 g/mol