■
■
Work through BLM 4-1: Balancing Chemical Equations Using Models/Skill Builder
with the students.
BLM 4-2: The Structure of the Language of Chemistry 1 Infomation Handout helps
students recognize the analogy between chemical equations and English sentences.
Common Misconceptions
Students may feel that they can balance equations by changing formulas or by inserting
numbers within formulas. The use of molecular models and rearranging the atoms in the
molecules will allow students to see why these methods cannot be used.
Solutions for Practice Problems
Student Textbook, pages 112, 113, 116, and 117
Student Textbook, page 114
Students should have no
trouble finding information on
Jan Baptista van Helmont on
the Internet, including the fact
that he is said to have been
the first to use the term gas.
He is also recognized as the
first scientist to suggest that
gases exist that are distinct
from air.
See Solutions Manual for solutions to Practice Problems.
Section Review Answers
Student Textbook page 118
1. Accept answers that incorporate the idea of elements and/or compounds interacting
to form other elements and/or compounds. Students may suggest everyday examples
such as: burning fuels; cooking of food; digesting food; rotting garbage; and rusting
iron.
2. (a) sulfur dioxide gas + oxygen gas → sulfur trioxide gas
SO2(g) + O2(g) → SO3(g)
2SO2(g) + O2(g) → 2SO3(g)
(b) sodium metal + water → hydrogen gas + sodium hydroxide
Na(s) + H2O() → H2(g) + NaOH(aq)
reaction is already balanced
(c) copper + hydrogen nitrate → copper(II) nitrate + nitrogen dioxide + water
Cu(s) + HNO3(aq) → Cu(NO3)2(aq) + NO2(g) + H2O()
Cu(s) + 4HNO3(aq) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O()
3. Oxygen gas has the formula of O2(g) . Changing the formula to O(g) changes the
product of the reaction instead of changing the number of particles of products.
4. (a) 4Al(s) + 3O2(g) → 2Al2O3(s)
(b) 2Na2S2O3(aq) + 4I2(aq) → 2NaI2(aq) + Na2S4O6(aq)
(c) 2Al(s) + Fe2O3(s) → Al2O3(s) + 2Fe(s)
(d) 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O()
(e) Na2O(s) + (NH4)2SO4(aq) → Na2SO4(aq) + H2O() + 2NH3(aq)
(f) C5H12() + 8O2(g) → 5CO2(g) + 6H2O(g)
5. Total mass of reactants = 0.58 g + 1.600 g + 40.32 g + 100.00 g = 142.50 g
This is the same mass as the total final mass of 142.5 g. Since mass has been
conserved, no atoms have been lost or added. The atoms present have just been
rearranged.
copper(II) sulfate + iron → iron(II) sulfate + copper
CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)
Student Textbook page 112
1. (a) calcium fluoride, CaF2
(b) hydrogen chloride, HCl;
barium sulfate, BaSO4
(c) calcium hydrogen
carbonate, Ca(HCO3)2
(d) water H2O; oxygen, O2
(e) sulfur trioxide, SO3
Student Textbook page 115
Changing the formula in order
to balance the equation would
show incorrect or nonexistent
products being formed.
Student Textbook page 117
2KClO3(s) → 2KCl(g) + 3O2(g)
Chapter 4 Classifying Reactions: Chemicals in Balance • MHR
141
black residue that results from the yellow flame shows that not all the carbon is
converted to carbon dioxide.
Solutions for Practice Problems
Student Textbook, pages 122, 123, and 124
See Solutions Manual for solutions to Practice Problems.
Unit Project Prep
Section Review Answers
Student Textbook page 125
Student Textbook page 125
1. (a) Be + O2 → BeO
2Be + O2 → 2BeO
(b) Li + Cl2 → LiCl
2Li + Cl2 → 2LiCl
(c) Mg + N2 → Mg3N2
3Mg + N2 → Mg3N2
(d) Al + Br2 → AlBr3
2Al + 3Br2 → 2AlBr3
(e) K + O2 → K2O
4K + O2 → 2K2O
2. (a) K2O → K + O2
2K2O → 2K + O2
(b) CuO → Cu + O2
2CuO → 2Cu + O2
(c) H2O → H2 + O2
2H2O → 2H2 + O2
(d) Ni2O3 → Ni + O2
2Ni2O3 → 2Ni + 3O2
(e) Ag2O → Ag + O2
2Ag2O → 4Ag + O2
3. (a) Sn(OH)4(s) → SnO2(s) + H2O()
Sn(OH)4(s) → SnO2(s) + 2H2O() decomposition
(b) Cl2(g) + I2(s) → ICl3(s)
3Cl2(g) + I2(s) → 2ICl3(s) synthesis
4. C4H9OH() + O2(g) → CO2(g) + H2O(g)
C4H9OH() + 6O2(g) → 4CO2(g) + 5H2O(g)
5. HgO(s) → Hg() + O2(g)
2HgO(s) → 2Hg() + O2(g) decomposition
6. Students should form an analogy with the reaction of sulfur trioxide and water to
form sulfuric acid, explained on page 121 of the student textbook. If they do some
research, students will find that the three key reactions through which nitrogen oxides
contribute to acid rain are as follows:
2NO2(g) + H2O() → HNO3(aq) + HNO2(aq)
NO(g) + NO2(g) + H2O() → 2HNO2(aq)
3NO2(g) + H2O() → 2HO3(aq) + NO(g)
Accept any reasonable answers that indicate nitrogen oxides react with water to form
acids containing nitrogen, hydrogen, and oxygen.
Hydrocarbons undergo
combustion reactions, i.e., they
burn readily in air. Therefore, a
warning on lawnmower fuel
would indicate that it is
flammable, and should be kept
away from open flames and
sparks.
Chapter 4 Classifying Reactions: Chemicals in Balance • MHR
143
Cu(s) + HNO3(aq)
Cu(NO3)2(aq) +2NO2(g) +2H2O( )
+
2Na(OH)(aq)
2Cu(OH) 2(aq)
+
2NaNO3(aq)
Cu(s) + H2O( )
+
H2 SO4(aq)
CuSO4(aq) + H2O( )
Zn(s)
Cu(s) + ZnSO4(aq)
Assessment and Evaluation
ThoughtLab/
ExpressLab/
Investigation
Investigation 4-C:
From Copper to
Copper,
pages 138 –139
Curriculum
Expectations
Assessment
Tool/Technique
Achievement
Chart Category
Learning Skills
Overall Expectations
■ [MCB V.02] carry out laboratory studies of
chemical reactions, analyse chemical reactions
in terms of the type of reaction and the reactivity
of starting materials, and use appropriate
symbols and formulae to represent the structure
and bonding of chemical substances
■
■
■
Specific Expectations
Developing Skills of Inquiry and Communications
■ [MCB 2.06] predict the products of, and write
chemical equations to represent, synthesis,
decomposition, substitution, and double
displacement reactions, and test the predictions
through experimentation
Rubric for
Investigation 4-C
(see
“Assessment
and Evaluation”
in the front
matter of
Teacher’s
Resource
CD-ROM)
Inquiry
■
Teamwork
Organization
Section Review Answers
Student Textbook pages 140 –141
1. (a)
(b)
(c)
(d)
(e)
(f)
2. (a)
(b)
(c)
(d)
Li + H2O → LiOH + H2
Sn + FeCl2 → NR
F2 + 2KI → 2KF + I2
Al + MgSO4 → NR
Zn + CuSO4 → Cu + ZnSO4
2K + 2H2O → 2KOH + H2
3NaOH(aq) + Fe(NO3)3(aq) → Fe(OH)3(s) + 3NaNO3(aq)
Cu(OH)2(aq) + 2HCl(aq) → CaCl2(aq) + H2O()
K2CrO4(aq) + NaCl → NR
K2CO3(s) + H2SO4(aq) → K2SO4(aq) + H2O() + CO2(g)
Chapter 4 Classifying Reactions: Chemicals in Balance • MHR
151
UNIT 1 Chapter 4 CLASSIFYING REACTIONS: CHEMICALS IN BALANCE
3. (a) The reaction proceeds as a double displacement reaction producing NH4OH as
Unit Project Prep
one of the products. However NH4OH decomposes to produce H2O and NH3.
Student Textbook page 140
(b) (NH4)2SO4(aq) + 2KOH(aq) → 2NH3(g) + 2H2O() + K2SO4(aq)
Students will find many
different warnings. For
example, the label on chlorine
bleach warns that the liquid
should not mixed with other
products. Acids will cause
chlorine bleaches to
decompose releasing chlorine
gas, which is corrosive and
poisonous.
2HCl + NaClO →
H2O + NaCl + Cl2
Chlorine bleach and ammonia
cleaners react to produce
nitrogen chloride, which is
poisonous.
NH3 + 6NaClO →
2NCl3 + 6NaOH
incomplete combustion
single displacement
double displacement
combustion
decomposition
synthesis
decomposition
5. (a) The reactions are:
CO2(g) + H2O() → H2CO3(aq)
H2CO3(s) + CaOH(aq) → CaCO3(s) + H2O()
(b) In the world, the supply of carbon dioxide is relatively so large that the amounts
lost by the process of concrete absorption is negligible, so scientists neglected to
consider this reaction. In the sealed biosphere, the large amount of concrete
absorbed a significant amount of the small supply of carbon dioxide in the system.
(c) Students may suggest that a building material other than concrete could have been
used.
6. Copper + silver nitrate → silver + copper nitrate.
Cu(s) + 2AgNO3(aq) → 2Ag(s) + Cu(NO3)2(aq) single displacement reaction
4. (a)
(b)
(c)
(d)
(e)
(f)
(g)
4.4 Simple Nuclear Reactions
Student Textbook pages 142 –148
Introduction
This section provides a brief introduction to nuclear reactions including alpha, beta and
gamma decay along with nuclear fission and fusion. Students will be introduced to the
rules used in balancing nuclear equations and use them to write balanced equations for a
number of transformation reactions. The section concludes with a brief look at nuclear
fission and nuclear fusion.
Chemistry Background
Student Who Need Extra Help:
To model nuclear reactions
that involve small elements,
students can use pieces of
paper of plastic disks of
different colours to represent
the protons and neutrons. The
manipulatives will help
students keep track of the
nuclear particles and to
understand the rules for
nuclear equations.
152
The discovery of radioactivity paved the way to the discovery of the atomic nucleus, the
modern atomic model (quantum mechanical model of the atom) and ultimately the
explanation for radioactivity and nuclear reactions. As understanding of nuclear reactions
increased, the amount of energy of the nucleus was harvested first for war (nuclear
bombs) and then for peaceful uses (e.g. CANDU reactor for electrical energy
production). Nuclear isotopes are used in medicine to treat cancer, image bones and
organs, study metabolism, and various other body functions. Nuclear decay is used to
date artifacts and determine the geological age of rocks. Nuclear reactions have allowed
even more elements to be added to the periodic table.
Teaching Strategies
■
Start your presentation with a video clip of a nuclear reaction. The simulation of a
nuclear blast at the beginning of the new Godzilla movie is a good example that you
could use if your school has the rights to show commercial videos. Use the video to
MHR • Unit 1 Matter and Chemical Bonding
■
■
■
lead a class discussion on nuclear reactions, including their representation in popular
culture and the media. The MediaLink on page 142 of the student textbook provides
some topics for discussion.
Define and give examples of alpha decay, beta decay and gamma radiation. Distribute
BLM 4-3: Radioactivity and Nuclear Reactions/Information Handout for students’
reference.
Soap bubbles can be used to illustrate fission and fusion. A large soap bubble held by
a wand at each side can be slowly pulled apart into two or more bubbles with one or
more small bubbles being produced as well. These small bubbles can represent the
neutrons that are released in fission. Two small bubbles being brought together can
simulate the process of fusion.
At the end of this section, students should know how to balance simple nuclear
equations. Practice is provided in the form of Practice Problems within the section,
Section Review questions, Chapter 4 Review questions, and Unit 1 Review questions.
Problems 26–28 on page 648 of the student textbook also deal with writing and
balancing nuclear equations.
Solutions for Practice Problems
Student Textbook, pages 143, 144, and 147
See Solutions Manual for solutions to Practice Problems.
Student Textbook page 142
Students will come up with
such popular culture
references as the Incredible
Hulk characters, who was
created by the exposure to
gamma rays, the new Godzilla
movie, and 1950’s horror
movies such as The Incredible
Shrinking Man. Radioactivity
and nuclear reactions have a
bad reputation because of
well-known and disastrous
incidents such as the nuclear
bombing of Hiroshima and
Nagasaki in Japan at the end
of World War II, and reactor
accidents such as Three Mile
Island and Chernobyl.
Section Review
Student Textbook pages 147–148
1. In alpha decay, a large nucleus releases a helium nucleus consisting of two protons
and two neutrons. The mass number of the large nucleus decreases by 4 and the
atomic number decreases by 2.
238
234
4
92U → 90Th + 2He
238
92U
4
2He
234
90Th
In beta decay, a nucleus releases an electron, and a neutron is converted into a
proton, increasing the atomic number of the atom by 1.
40
40
0
19K → 20Ca + −1e
40
19K
40
20Ca
0
-1e
Chapter 4 Classifying Reactions: Chemicals in Balance • MHR
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UNIT 1 Chapter 4 CLASSIFYING REACTIONS: CHEMICALS IN BALANCE
In gamma decay, an excited nucleus lowers its energy by releasing electromagnetic
radiation such as gamma-rays. The gamma radiation often accompanies other forms
of radiation.
47
47
0
0
20Ca → 21Sc + −1e + 0γ
In nuclear fusion, two small nuclei combine to form a larger nucleus.
3
2
4
1
1H + 1H → 2He + 0n
2
1H
3
1H
4
2He
1n
0
In nuclear fission, neutron bombardment causes a large nucleus to split into smaller
nuclei.
235
93
1
140
1
92U + 0n → 56Ba + 36Kr + 30n
140
56Ba
neutron
235
92 U
nucleus
233
1
2. (a) 232
90Th + 0n → 90Th
nucleus
93
36Kr
3 released
neutrons
nucleus
nuclear fusion
beta decay
(b)
alpha decay
(c)
alpha decay
(d)
1
+ 30n
nuclear fission
(e)
nuclear fusion
(f)
3. The release of hot water into a lake is a form of pollution known as heat pollution.
The hot water warms the lake water, decreasing the amount of dissolved oxygen. This
reduces the oxygen available for fish, which kills them or causes them to move out of
the area. For example, trout need high levels of dissolved oxygen to survive. Plant
growth can be stimulated by the warm water, which can lead to increased bacterial
growth and a further reduction in oxygen levels. The overall effect leads to premature
eutrophication or aging of a water body.
4. Gamma rays are a form of radiation (energy), so their emission does not significantly
affect the masses of the products and reactants.
218
4
5. (a) 222
86Rn → 84Po + 2He ; alpha decay
(b) 21H + 31H → 42He + 10n; fusion
0
214
(c) 214
83Bi → −1e + 84Po; beta decay
92
1
144
(d) 235
92U + 0n → 36Kr + 56Ba ; fission
214
4
(e) 218
84Po → 82Pb + 2He; alpha decay
233
233
0
91Pa → 92U + −1e
226
222
4
88Ra → 86Rn + 2He
210
206
4
83Bi → 81Ti + 2He
235
90
143
1
92U + 0n → 38Sr + 54Xe
6
2
4
3Li + 1H → 22He
154
MHR • Unit 1 Matter and Chemical Bonding
90
1
(f) 90
38Sr → 39Y + −1e ; beta decay
Chapter 4 Review Answers
Student Textbook pages 149–151
Answers to Knowledge/Understanding Questions
1. A chemical reaction is usually accompanied by one or more of the following
phenomena: a change in properties, a colour change, formation of a precipitate,
formation of a gas, change of odour, and presence of a flame or other form of energy.
2. The color of paint comes from pigmented solids suspended in a liquid medium.
When different paints are mixed, the solids do not react, but the eye interprets the
mixture of particles as a differently-colored new color.
3. Balancing a chemical equation satisfies the law of conservation of mass, since the
same number of each type of atom is present in the reactants and in the products.
Since a specific mass is associated with each type of atom, mass is conserved.
4. (a) PdCl2(aq) + 2HNO3(aq) → Pd(NO3)2(aq) + 2HCl(aq)
(b) Cr(s) + 2HCl(aq) → CrCl2(aq) + H2(g)
(c) 4FeO(s) + O2(g) → 2Fe2O3(s)
5. decomposition; single displacement; synthesis
6. (a) H2(g) + CuO(s) → Cu(s) + H2O(g) : single displacement
(b) 16Ag(s) + S8(s) → 8Ag2S(s) : synthesis
(c) C4H8(g) + 6O2(g) → 4CO2(g) + 4H2O(g) : combustion
(d) NH3(g) + HCl(g) → NH4Cl(s) : synthesis
(e) 2Mg(s) + O2(g) → 2MgO(s) : synthesis, combustion
(f) RbCl(s) + 2O2(g) → RbClO4(s) : synthesis, combustion
(g) 2Cu2S(s) + 3O2(g) → 2Cu2O(s) + 2SO2(g) : combustion
7. Analysis of a solubility chart allows one to determine if a precipitate will form in a
double displacement reaction and to identify and predict what the precipitate will be.
8. The reaction is a decomposition reaction.
9. (a) sodium hydroxide + iron(III) nitrate acid → iron hydroxide + sodium nitrate
2NaOH(aq) + Fe(NO3)2(aq) → FeOH2(s) + 2NaNO3(aq)
antimony
+ chlorine → antimony trichloride
(b)
2Sb + (s) + 3Cl2(g) → 2SbCl3(s)
(c) mercury + oxygen → mercury(II) oxide
2Hg() + O2(g) → 2HgO(s)
(d) ammonium nitrite → nitrogen + water
NH4NO2(s) → N2(g) + 2H2O()
(e) aluminum + zinc sulfate → zinc + aluminum sulfate
2Al(s) + 3ZnSO4(aq) → 3Zn(s) + Al2(SO4)3(aq)
10. (a) The equation shows a double displacement reaction.
(b) Pb(NO3)2(aq) + K2CrO4(aq) → PbCrO4(s) + 2KNO3(aq)
11. An oxide of a non-metal generally forms an acid when it reacts with water.
SO3(g) + H2O() → H2SO4(aq)
12. An oxide of a metal generally forms a base when it reacts with water.
K2O(s) + H2O() → 2KOH(aq)
13. (a) 21H + 31H → 42He + 10n; fusion
239
0
(b) 239
92U → 93Np + −1β ; beta decay
Chapter 4 Classifying Reactions: Chemicals in Balance • MHR
155
UNIT 1 Chapter 4 CLASSIFYING REACTIONS: CHEMICALS IN BALANCE
239
0
(c) 239
93Np → 94Pu + −1β ; beta decay
234
4
0
(d) 238
92U → 90Th + 2He + 20γ ; alpha decay and gamma radiation
BaCl2(aq) + Na2CO3(aq) → BaCO3(s) + 2NaCl(aq)
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g)
PCl5(s) → PCl3() + Cl2(g)
3Mg(s) + Fe2O3(s) → 3MgO(s) + 2Fe(s)
Ca(s) + Cl2(g) → CaCl2(s)
15. Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)
Note: this is a redo x reaction, so students will not be able to classify it. Students
should note that the reaction does not fit the classification they know.
16. calcium carbonate + hydrochloric acid →
calcium chloride + carbon dioxide + water
This is a double displacement reaction followed by a decomposition reaction.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O()
14. (a)
(b)
(c)
(d)
(e)
(f)
Answers to Inquiry Questions
17. The zinc will react with the hydrochloric acid producing hydrogen gas and copper
chloride solution, leaving only the copper “skin” of the penny as a solid.
18. The earring will get wet. The silver will not react with the hydrochloric acid because
the silver is less reactive than acidic hydrogen.
Answers to Communication Questions
19. Chemicals are stored in tightly sealed bottles to protect them from components of air
such as oxygen, water or carbon dioxide. Chemicals are kept out of sunlight so that
the radiation will not facilitate any reactions such as decomposition.
20. Students should indicate that a burning cigarette is an example of combustion, which
consumes oxygen. They should note that air is only 20% oxygen, compared to pure,
100% oxygen, and that the reaction would be more violent when there is more
reactant available.
21. Gasoline is very volatile, meaning the gasoline readily evaporates. The mixture of
gasoline vapour and air can ignite and explode from a lit cigarette. Students should
note that gasoline is a hydrocarbon that readily undergoes combustion in air.
22. (a) Add sodium chloride to precipitate the silver as silver chloride.
(b) Add a more reactive metal such as zinc to displace the silver from the solution.
Answers to Making Connections Questions
23. (a) Two ways to produce calcium carbonate are: decomposing of calcium carbonate
by heating
CaCO3(s) → CaO(s) + CO2(g)
or burning calcium in oxygen to produce calcium oxide in a synthesis reaction.
2Ca(s) + O2(g) → 2CaO(s)
(b) calcium oxide + water → calcium hydroxide
CaO(s) + H2O() → Ca(OH)2(s)
Both calcium oxide and calcium hydroxide are bases and are therefore corrosive.
156
MHR • Unit 1 Matter and Chemical Bonding