CHAPTER 3
ANSWER KEY
BLM 3-1, Chemical or Physical Change?/
Reinforcement
BLM 3-2, Using a Solubility Table/Skill
Builder
Goal: Students demonstrate their ability to distinguish
between chemical and physical changes.
Goal: Students predict solubility using a solubility table.
Answers
Answers
Chemical
or
physical? Explanation
Change
A sheet of paper is physical Only the shape of the
change
paper changed. No new
crumpled into a
substances were formed.
ball.
A sheet of paper is chemical The paper underwent a
change
chemical reaction to form
set on fire and
new substances (carbon,
burns to ashes.
carbon dioxide, carbon
monoxide, and water).
chemical The rust that formed is a
Steel wool is
new substance.
placed in a glass of change
salty water. The
steel wool rusts.
A sheet of flexible, chemical The change in colour to
yellow is a clear
colourless plastic is change
giveaway that a chemical
left outside, in
reaction took place. The
bright sunlight, and
change in the property of
becomes yellow
flexibility suggests that a
and brittle over
new compound was
time.
formed. The light
allowed the plastic to
react with oxygen to
form different
compounds.
physical The sugar dissolved into
A teaspoon of
change
the water to form a
white sugar
solution, but did not
(sucrose) dissolves
undergo a chemical
in a glass of warm
reaction. No new
water.
substances were formed.
Vinegar is poured chemical The fizzing indicates the
formation of a gaseous
over a teaspoon of change
substance, carbon
baking soda. The
dioxide.
white powdered
baking soda fizzes,
and bubbles form.
physical A state change has
A red-hot nail is
occurred, but no new
inserted into a large change
substances are formed.
block of ice. Steam
is formed as the nail
contacts the block,
and water flows
away from the nail.
Answers are in boldface.
1.
Name
sodium
chloride
Formula
NaCl
High or low
Cation Anion solubility?
Na+
Cl–
high
lithium
iodide
LiI
Li+
I–
high
magnesium Mg(ClO3)2
chlorate
Mg2+
ClO3–
high
strontium
hydroxide
Sr(OH)2
Sr2+
OH–
high
barium
carbonate
BaCO3
Ba2+
CO32–
low
2.
Name
aluminium hydroxide
Formula
Al(OH)3
High or low
solubility?
low
ammonium chloride
NH4Cl
high
potassium sulfide
K2S
high
molybdenum(V) chlorate Mo(ClO3)5
high
lead(II) acetate
Pb(CH3COO)2
high
copper (II) iodide
CuI2
high
iron(II) carbonate
FeCO3
low
calcium sulfite
CaSO3
low
barium phosphate
Ba3(PO4)2 (s)
low
palladium (II) bromide
PdBr2
high
mercury(I) iodide
HgI
low
strontium sulfate
SrSO4
low
BLM 3-3, Recognizing Reactions of Ionic
Compounds in Solution/Science Inquiry
Goal: Students observe the formation of a precipitate, and
identify the ions that have combined.
Answers
Answers for Investigation 3-A: Recognizing Reactions of
Ionic Compounds in Solution are provided in the
SCIENCEFOCUS 10 Teacher’s Resource.
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CHAPTER 3
ANSWER KEY
BLM 3-4, Endothermic and Exothermic
Reactions/Reinforcement
Goal: Students demonstrate their understanding of
exothermic and endothermic reactions.
Answers
1.
Description of
chemical reaction
A piece of paper is
ignited and burns with
a bright flame.
Pentaborane (a
colourless liquid),
B5H9, reacts violently
with oxygen gas to
form solid diborane,
B2O3, and water,
typically bursting into
flame and often
exploding.
Pure iron metal is
formed and carbon
dioxide is released
when iron(III) oxide
ore is heated to a very
high temperature in
the presence of solid
carbon.
Sodium hydroxide
solution and
hydrochloric acid
solution are mixed.
The temperature of
the mixture increases.
Mixing ammonium
thiocyanate and
barium hydroxide
octahydrate in a
beaker causes water
on the outside of the
beaker to freeze.
The high temperature
in an oven causes
baking soda (sodium
hydrogencarbonate) to
break down into
carbon dioxide, water,
and sodium carbonate.
Endothermic
or
exothermic? Explanation
Heat and light are
exothermic
emitted.
exothermic
endothermic
exothermic
Bursting into
flames and
explosions are
both energy
emissions.
High
temperatures are
required to form
the new
substances.
Heat is emitted.
2. (a) The energy that is released in an exothermic
reaction results from the difference between the
energy absorbed when reactant bonds break and
the energy released when product bonds form. In
an exothermic reaction, the energy that is required
to break bonds is less than the energy that is
released to form bonds. The energy that is
released is absorbed by the surroundings.
(b) The energy that is absorbed by an endothermic
reaction comes from the surroundings. Energy is
required by the reaction because the energy that is
required to break bonds is greater than the energy
that is released to form bonds.
3. The initial spark is an endothermic requirement, but
the overall reaction is exothermic since heat and light
are the end products. Many exothermic reactions (such
as combustion reactions) require some initial energy
input in order to proceed.
BLM 3-5, Modelling Chemical Reactions/
Science Inquiry
Goal: Students classify chemical reactions, based on their
equations.
Answers
Answers to the questions for Find Out Activity: Modelling
Chemical Reactions are provided in the SCIENCEFOCUS
10 Teacher’s Resource.
BLM 3-6, Balancing Equations/Skill
Builder
Goal: Students practise balancing and classifying skeleton
equations.
Answers
endothermic
Heat is absorbed
from the
surroundings.
endothermic
Heat is absorbed
from the
surroundings to
cause the reaction
to occur.
1. (a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
2. (a)
(b)
4K(s) + O2(g) → 2K2O(s)
P4(s) + 10Cl2(g) → 4PCl5(s)
8Cu(s) + S8(s) → 8CuS(s)
2Mg(s) + O2(g) → 2MgO(s)
4Fe(s) + 3O2(g) → 2Fe2O3(s)
4P4(s) + 5S8(g) → 8P2S5(s)
2C(s) + O2(g) → 2CO(g)
N2(g) + 2O2(g) → 2NO2(g)
6Li(s) + N2(g) → 2Li3N(s)
S8(s) + 8O2(g) → 8SO2(g)
4Al(s) + 3O2(g) → 2Al2O3(s)
8Zn(s) + S8(s) → 8ZnS(s)
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CHAPTER 3
3.
4.
5.
6.
7.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(a)
(b)
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(a)
(b)
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
8. (a)
(b)
9. (a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
ANSWER KEY
2NaCl(s) → 2Na(s) + Cl2(g)
CaBr2(s) → Ca(s) + Br2(l)
CCl4(l) → C(s) + 2Cl2(g)
2NCl3 (g) → N2(g) + 3Cl2(g)
P4O10(s) → P4(s) + 5O2(g)
2Ag2O(s) → 4Ag(s) + O2(g)
2HCl(aq) → H2(g) + Cl2(g)
2KI(s) → 2K(s) + I2(s)
2AlCl3(s) → 2Al(s) + 3Cl2(g)
2CuO(s) → 2Cu(s) + O2(g)
2Rb2O(s) → 2Rb(s) + O2(g)
CaCl2(s) → Ca(s) + Cl2(g)
6K(s) + 2H3PO4(aq) → 2K3PO4(aq) + 3H2(g)
2Fe(s) + 3H2S(aq) → Fe2S3(s) + 3H2(g)
Cl2(g) + MgBr2(aq) → MgCl2(aq) + Br2(aq)
Cu(s) + Ag2CO3(s) → CuCO3(s) + 2Ag(s)
Br2(g) + KI(aq) → I2(aq) + KBr(aq)
3Mg(s) + Zn3(PO4)2(s) → Mg3(PO4)2(s) + 3Zn(s)
3K(s) + Al(NO3)3(aq) → Al(s) + 3KNO3(aq)
Ca(s) + 2H2O(l) → Ca(OH)2(s) + H2(g)
2Na(s) + H2SO4(s) → Na2SO4(aq) + H2(g)
K(s) + H2O (l) → KOH(aq) + H2(g)
3Ag(s) + Au(NO3)3(aq) → Au(s) + 3AgNO3(aq)
Cu(s) + PbSO4(aq) → Pb(s) + CuSO4(aq)
Na2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2NaCl(aq)
2HNO3(aq) + Ba(OH)2(aq) → 2H2O (l) + Ba(NO3)2(aq)
3Na2CO3(aq) + 2Fe(NO3)3(aq) → Fe2(CO3)3(s) +
6NaNO3(aq)
3CaCl2(aq) + 2K3PO4(aq) → Ca3(PO4)2(s) + 6KCl(aq)
Al2(SO4)3(aq) + 3Ba(OH)2(aq) → 2Al(OH)3(s) +
3BaSO4(s)
2NaOH(aq) + H2SO4(aq) → 2H2O (l) + Na2SO4(aq)
2Na3PO4(aq) + 3Ag2SO4 (s) → 3Na2SO4(aq) +
2Ag3PO4(s)
Na2CrO4(aq) + Cu(NO3)2(aq) → 2NaNO3(aq) +
CuCrO4(aq)
H3PO4(aq) + 3KOH(aq) → 3H2O (l) + K3PO4(aq)
Na2CO3(aq) + 2HNO3(aq) → H2CO3(aq) + 2NaNO3(aq)
NaOH(aq) + HCl(aq) → H2O(l) + NaCl(aq)
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
2C6H14(g) + 19O2(g) → 12CO2(g) + 14H2O(g)
2C8H18(g) + 25O2(g) → 16CO2(g) +18H2O(g)
2C2H2(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
2ZnS(s) + 2O2(g) → 2ZnO(s) + SO2(g)
4CH3NO2(l) + 7O2(g) → 4CO2(g) + 6H2O(g) +
4NO2(g)
4NH3(g) + 5O2(g) → 2NO2(g) + 6H2O(g)
2C2H5SH(g) + 9O2(g) → 4CO2(g) + 6H2O(g) +
2SO2(g)
10. (a) C25H52(s) + 38O2(g) → 25CO2(g) + 26H2O(l)
(b) 2C12H22O11(s) + 24O2(g) → 24CO2(g) + 22H2O(l)
11.
Reaction
Classification
3Li (s) + AlCl3(aq) → Al (s) + 3LiCl(aq)
SR
2NH3(g) → 3N2(g) + 3H2(g)
D
2K (s) + Br2(l) → 2KBr(s)
F
2C10H22(l) + 31O2(g) → 20CO2(g) +
C
22H2O(g)
2NH4OH (aq) + H2CO3(aq) → 2H2O(l) +
DR
(NH4)2CO3(aq)
2H2O (l) → 2H2(g) + O2(g)
D
2Al(s) + 3Cl2(g) → 2AlCl3(s)
F
2Zn(s) + SnF4(aq) → Sn(s) + 2ZnF2(aq)
SR
BLM 3-7, Putting It Together: Classifying
Chemical Reactions/Science Inquiry
Goal: Students identify reactants and products, and
classify chemical reactions.
Answers
Sample predictions, observations, and answers for
Investigation 3-D: Putting It Together: Classifying
Chemical Reactions are provided in the SCIENCEFOCUS
10 Teacher’s Resource.
BLM 3-8, Observing Single and Double
Replacement Reactions/Investigation
Goal: Students demonstrate their ability to predict the
products of chemical reactions.
Answers
Tips
•
•
•
Have students complete the Hypothesis and
Predictions sections and their data table as homework.
Ensure students clean up the stations after each trial so
that the station is ready for the next group.
Copper(II) chloride and cobalt(II) chloride are toxic.
Ensure that these substances are not banned from
use in schools by your school board.
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CHAPTER 3
ANSWER KEY
Hypothesis Answers
2NaOH(aq) + CoCl2(aq) → Co(OH)2(s) + 2NaCl(aq)
NaCH3OO(aq) + HCl(aq) → CH3COOH(aq) + NaCl(aq)
Mg(s) + 2HCl(aq) → H2(g) + MgCl2 (aq)
3Ca(NO3)2(aq) + 2Na3PO4(aq) → 6NaNO3(aq) +
Ca3(PO4)2(s)
5. Ca(s) + H2O(l) → Ca(OH)2(s) + H2(g)
6. 2Al(s) + 3 CuCl2(aq) → 2AlCl3(aq) + 3Cu(s)
1.
2.
3.
4.
Station
Observations
6
A blue solution of
copper(II) chloride
should react with the
aluminium metal to
produce a colorless
solution and copper
metal.
Prediction Answers
Students should be able to predict most of the observations
listed below. They will likely not predict the colour
changes for stations 1 and 6, and they may not realize that
CH3COOH(aq) is vinegar and will have the characteristic
odour of acetic acid.
Notes for instructors
• The copper produced
will tend to “plate”
itself onto the
aluminum foil.
Bubbles and some
heat may also result.
• Copper(II) chloride is
toxic. Check with
your lab technician or
school board to
ensure the substance
is not banned from
schools in your area.
Analysis
Sample Observations
Station
Observations
1
The cobalt(II) chloride
solution should be
pink in color and the
reaction should
produce a colorless
solution and a
precipitate (copper).
2
Two colorless
solutions should mix
to form a colorless
solution with a vinegar
smell from the acetic
acid that forms.
3
The magnesium metal
should react to form a
colorless solution and
bubbles of hydrogen
gas should form. The
collected gas should
“pop” when a glowing
splint is introduced
into the large test tube.
4
Two colorless
solutions should react
to form a precipitate.
5
The calcium metal
should react to
produce a colorless
solution and bubbles
of hydrogen gas
should form. The
collected gas should
“pop” when a glowing
splint is introduced
into the large test tube.
Notes for instructors
• Cobalt(II) chloride is
toxic. Check with
your lab technician or
school board to
ensure the substance
is not banned from
schools in your area.
• This is a fairly subtle
change.
• Remind students to
“waft” the smell to
their noses.
• This is an exothermic
reaction.
1. Students should have observed the pink colour of the
solution becoming colourless. This observation shows
that the copper ions are reacting to form copper metal.
2. Students should recognize the smell as “vinegary.” If
they predicted the reaction would form acetic acid,
CH3COOH(aq), they can explain that acetic acid is the
acid in white household vinegar.
Conclude and Apply
3. Students may not have predicted the colour changes,
but should be able to explain that the ions of cobalt(II)
and copper(II) are coloured, but the colour disappears
as the ions react and form solid metals.
4. (a) The correct equations are listed above in the
hypothesis section.
(b) Students should state how the observations
provided evidence for the predicted products. For
example, the splint test should have confirmed the
presence of hydrogen for stations 3 and 5.
(c) The reactions at stations 1, 2, and 4 are double
replacement reactions. The reactions at stations 3,
5, and 6 are single replacement reactions.
BLM 3-9, Chemical Equations Quiz/
Assessment
Goal: Students demonstrate their ability to balance and
classify chemical equations.
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CHAPTER 3
ANSWER KEY
Answers
Reaction
Classification
Ni(s) + 2HCl(aq) → NiCl2(aq) + H2(g)
SR
(d) 0.0143 mol
(e) 62.3 mol
(f) 2.64 mol
4. Answers are in boldface.
(a)
SR
2Au(CN)3(aq) + 3Zn(s) → 2Au(s)
+ 3Zn(CN)2(aq)
2Na
O2(g) + 2Be(s) → 2BeO(s)
8.0 mol
8.0 mol
4.0 mol
8.0 mol
0.20 mol
0.20 mol
0.10 mol
0.20 mol
9.60 mol
9.60 mol
4.80 mol
9.60 mol
16.0 mol
16.0 mol
16.0 mol
16.0 mol
F
DR
2FeCl3(aq) + 3Na2SO3(aq) → 6NaCl(aq)
+ Fe2(SO3)3(s)
C
2C8H18(g) + 25O2(g) → 16CO2 (g) +
18 H2O(g)
DR
(NH4)2S(aq) + Mn(NO3)2(aq) →
2NH4NO3(aq) + MnS(s)
P4(s) + 6F2(g) → 4PF3(l)
F
DR
Al2(SO4)3(aq) + 2Na3PO4(aq) →
3Na2SO4(aq) + 2AlPO4(s)
O
6CO2(g) + 6H2O(l) → C6H12O6(l) + 6O2(g)
2H3(PO4)(aq) + 3Cu(OH)2(aq) → 6H2O(l)
DR
+ Cu3(PO4)2(s)
Sr(OH)2(aq) + H2SO4(aq) → 2H2O(l)
DR
+ SrSO4(s)
2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(g)
C
BLM 3-10, The Mole/Problem Solving
Goal: Students practise working with the mole.
Answers
Answers are in boldface.
1. (a) 3 mol of magnesium chloride, MgCl2, contains 3
mol of magnesium ions and 6 mol of chloride
ions.
(b) 2 mol of propane, C3H8, contains 1.204 × 1024
molecules of propane, 3.612 × 1024 atoms of
carbon, and 9.632 × 1024 atoms of hydrogen.
(c) In 3.01 × 1024 molecules of the molecular
compound sucrose, C12H22O11, there are 3.612 ×
1025 atoms of carbon, 6.622 × 1025 atoms of
hydrogen, and 3.311 × 1025 atoms of oxygen.
(d) In 3.54 mol of sucrose, C12H22O11, there are 42.5
mol of carbon atoms, 77.9 mol of hydrogen
atoms, and 38.9 mol of oxygen atoms.
2. (a) 206.98 g/mol
(b) 58.33 g/mol
(c) 142.05 g/mol
(d) 190.32 g/mol
3. (a) 0.210 mol
(b) 233 mol
(c) 0.169 mol
+ 2H2O
→ H2
+ 2NaOH
(b)
Al2(SO4)3
+ 6NH4OH → 2Al(OH)3 + 3(NH4)2SO4
3.0 mol
18.0 mol
6.0 mol
9.0 mol
0.33 mol
2.0 mol
0.66 mol
1.0 mol
0.500 mol
3.00 mol
1.00 mol
1.50 mol
BLM 3-11, Chapter 3 Test/Assessment
Goal: Students demonstrate their understanding of the
information presented in Chapter 3.
Answers
1. T
2. F: Most ionic substances that contain acetate ions
are soluble in water. (The exception is
AgCH3COO.)
3. F: The formation of new chemical bonds is always
an exothermic process.
4. T
5. T
6. (j)
7. (d)
8. (k)
9. (a)
10. (f)
11. chemical reaction
12. endothermic
13. open system
14. decomposition
15. molar mass
16. (a)
17. (d)
18. (c)
19. (d)
20. (c)
21. (b)
22. (c)
23. (a)
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CHAPTER 3
ANSWER KEY
24. (d)
25. (d)
26.
Name
Formula
High or low solubility?
silver bromide
AgBr
low
sodium sulfide
Na2S
low
ammonium chloride NH4Cl
high
lead(II) sulfate
PbS
low
calcium phosphate
Ca3(PO4)2 low
barium hydroxide
Ba(OH)2 high
27. Indications of a chemical reaction include a change in
odour or colour, the formation of a precipitate, the
formation of a gas, and the emission of energy in the
form of light, heat, or sound.
28. In an exothermic reaction, more energy is released
from the formation of bonds than is absorbed by the
breaking of bonds. In an endothermic reaction, the
opposite is true.
29. (a) The molar mass of ammonium sulfate is 132.17
g/mol.
(b) You were given 0.4994 mol of ammonium
sulfate.
(c) 0.4994 mol of ammonium sulfate corresponds to
3.01 × 1023 formula units of ammonium sulfate.
(d) The sample contains 3.995 mol of hydrogen
atoms.
(e) A precipitate forms. It is calcium sulfate, CaSO4.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
(b)
(c)
(a)
(d)
(d)
(a)
(a)
3214
2850
1479
1332
(a) 2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(g)
(b) The reaction is exothermic. Although a match is
required to initiate the combustion, a large
amount of energy is released in the form of heat
and light.
(c) The reaction is complete combustion. Because the
combustion takes place in pure oxygen, there is
sufficient oxygen for complete combustion to
occur. In an incomplete combustion reaction,
carbon monoxide and carbon would be produced.
(d) There are equal numbers of carbon atoms,
hydrogen atoms, and oxygen atoms on each side
of the equation. Atoms are not transformed,
destroyed, or created. Therefore, the mass of the
reactants is equal to the mass of the products.
(e) The molar mass of butane is 49.42 g/mol.
(f) 35.0 g of butane is 0.708 mol of butane.
BLM 3-12, Unit 1 Test/Assessment
Goal: Students demonstrate their understanding of the
information presented in Unit 1.
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
(a)
(b)
(d)
(c)
(a)
(b)
(c)
(b)
(c)
(b)
(d)
(d)
(b)
(d)
(a)
(d)
(d)
(b)
Copyright © 2004 McGraw-Hill Ryerson Limited. Permission to edit and reproduce this page is granted to the purchaser for use in her/his classroom. McGraw-Hill Ryerson shall not
be held responsible for content if any revisions, additions, or deletions are made to this page.