Chapter 9: Solutions and Their Reactions
Section 9.1: Reactions of Ions in Solution, pages 149–151
1. (i) formula equations
(ii) total ionic equations
(iii) net ionic equations
2. Figure 1
3. Table 2 Solubility of Compounds
Compound
Solubility (aq) or (s)
NaCl
(aq)
Ag2SO4
(s)
NaOH
(aq)
(NH4)2S
(aq)
4. a
5. A chemical equation is considered balanced when the same number of atoms for each element is present on
each side and the net electrical charge on both sides of the equation is the same.
6. False: Ions that do not participate in the reaction are called spectator ions.
7. 3 CaCl2(aq) + 2 K3PO4(aq) → Ca3(PO4)2(s) + 6 KCl(aq)
3 Ca+2(aq) + 6 Cl−(aq) + 6 K+(aq) + 2 PO43−(aq) → Ca3(PO4)2(s) + 6 K+(aq) + 6 Cl−(aq)
8. No, a reaction would not occur between barium nitrate, Ba(NO3)2, and water because both the products and
the reactants are soluble in water so they remain as ions.
9. Ions that appear on both sides of a total ionic equation remain unchanged during a chemical reaction.
10. The net ionic equation describes the chemical change that occurs in a reaction involving ions.
11. (a) Write the formula equation.
BaSO4 + K2S → BaS + K2SO4
Use the solubility table to determine what compound(s) would precipitate.
BaSO4(aq) + K2S(aq) → BaS(s) + K2SO4(aq)
Write the total ionic equation.
Ba2+(aq) + SO42−(aq) + 2 K+(aq) + S2−(aq) → BaS(s) + 2 K+(aq) + SO42− (aq)
Write the net ionic equation.
Ba2+(aq) + S2−(aq) → BaS(s)
(b) SO42−(aq) and 2K+(aq) are considered spectator ions.
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Chapter 9: Solutions and Their Reactions
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Section 9.2: Water Treatment, pages 152–153
1. Proper sanitation is one of the most important initial steps for improving water quality. It eliminates waterborne diseases such as cholera, which is caused by a bacterium that is spread by contaminated water.
2. Table 1 Types of Water Contaminants
Contaminant
Example
Source
physical
floating debris such as
littering by humans
plastic
biological
bacteria and viruses
exist naturally in water
chemical
consumer chemicals, ions
pollution of the
from mines
environment
3. Leachate is fluid that has passed through solid waste material and has extracted suspended or dissolved
substances from mines or dump sites.
4. False. Physical and biological, but not chemical contaminants form heterogeneous mixtures with water.
5. If you live near a coal mine, arsenic and cyanide are most likely to contaminate your water supply.
6. c
7. Hard water, especially when it comes in contact with soap, forms precipitates that can clog hot water pipes
as well as the heating elements of water heaters.
8. Flowcharts may vary. Answers should include the following information:
Water treatment process: Step 1: Collection. Step 2: Coagulation, flocculation, and sedimentation. Step 3:
Filtration. Step 4: Disinfection. Disinfectant used to kill micro-organisms. Step 5: Aeration. Substances mixed
with water to reduce taste and colour problems. Step 6: Softening. Substances added to reduce water hardness
by precipitating Ca2+ and Mg2+ ions.
Section 9.3: Chemical Analysis, page 154
1. Substances are identified by their physical or chemical properties.
2. Table 1 Chemical Analysis Test
Test method
Chemical analysis
pH
both
hormone concentration in blood sample
quantitative
nickel test paper
qualitative
breathalyzer
quantitative
3. When doing a qualitative analysis test, to ensure that the ions present are identified, the tests must be
performed in a specific order.
4. The filtrate is the clear liquid that remains after a mixture has been filtered.
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Chapter 9: Solutions and Their Reactions
9-2
5.
6. False. Spectroscopy is helpful in quantitative and qualitative analysis.
Section 9.4: Chemistry Journal: Drugs in Drinking Water, page 155
1. Answers may vary. Sample answer:
Figure 1
2. No, it is not a good idea to flush your mediations down the toilet because many of the drugs do find their
way into the water system.
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Chapter 9: Solutions and Their Reactions
9-3
3. Answers may vary. Sample answer: Some types of vitamins cannot be dissolved by the body and are
excreted in urine. Many types of fats are also insoluble in the body and are released as waste samples.
Section 9.5: Stoichiometry of Solutions, pages 156–157
1. Aqueous solutions allow chemists to control a variety of variables by making adjustments to temperature
and/or concentrations.
2. a
3. Answers may vary. Sample answer: Chemicals mix more completely when they are dissolved, which results
in a faster reaction. Allowing reactions to occur in solution makes it easier to control how quickly the reactions
actually occur.
4. Convert the known quantities of chemicals used to amounts. Convert amount of given substance to amount
of required substance. Convert amount of required substance to quantity of substance.
5. False. Chemicals mix more completely when they are dissolved, resulting in faster reactions.
6. Given: cAgNO = 0.25 mol/L ; cNaCl = 0.05 mol/L ; VNaCl = 0.250 L
3
Required: volume of 0.25 mol/L silver nitrate, VAgNO
3
n
Analysis: c =
V
Solution:
Step 1: Write a balanced equation for the reaction.
AgNO3(aq)
+
NaCl(aq) → AgCl(s) + NaNO3(aq)
cAgNO3 = 0.25 mol/L cNaCl = 0.05 mol/L
VNaCl = 0.250 L
VAgNO3
Step 2: Determine the amount of NaCl by rearranging the equation.
n
V
= cNaClVNaCl
c=
nNaCl
mol
! 0.250 L
L
= 0.0125 mol (one extra digit carried)
= 0.05
nNaCl
Step 3: Determine the amount of silver nitrate.
nAgNO3 = 0.0125 mol NaCl !
1 mol AgNO3
1 mol NaCl
nAgNO3 = 0.0125 mol (one extra digit carried)
Step 4: Determine the volume of silver nitrate by rearranging the equation.
VAgNO3 =
nAgNO3
cAgNO3
0.0125 mol
mol
0.25
L
= 0.050 L
=
VAgNO3
Statement: The minimum volume of 0.25 mol/L silver nitrate required to react completely with the sodium
ions is 0.050 L.
7. BaCl2(s) → Ba2+(aq) + 2 Cl–(aq)
8. Researchers consider calcium chloride to be a good electrolyte because after it dissolves in water, the
resulting solution conducts electricity well.
9. c
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Chapter 9: Solutions and Their Reactions
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10. Given: mPb (PO
3
4 )2
= 30.5 g ; VPb3 (PO4 )2 = 525 mL
Required: amount concentrations of lead and phosphate ions, cPb and cPO
2+
4
3!
Solution:
Step 1: Convert given volume to litres.
VPb3 (PO4 )2 = 525 mL !
1L
1000 mL
VPb3 (PO4 )2 = 0.525 L
Step 2. Determine the amount of solute from the given mass of solute.
nPb (PO ) = 30.5 g !
3
4 2
1 mol
811.54 g
nPb (PO ) = 0.0375 83 mol (two extra digits carried)
3
4 2
Step 3. Determine the amount concentration of the solution.
cPb (PO ) =
3
4 2
nPb (PO
3
4 )2
VPb (PO
4 )2
3
0.0375 83 mol
0.525 L
= 0.0715 87 mol (two extra digits carried)
=
cPb (PO
3
4 )2
Step 4. Write a dissociation equation listing the calculated amounts and the required values.
Pb3(PO4)2
→
3 Pb2+(aq) + 2 PO43–(aq)
3
cPO 3!
cPb2+
cPb (PO ) = 0.0715 87 mol
4 2
4
Step 5. Convert the concentration of Pb3(PO4)2 into concentration of the ions.
cPb2+ = 0.071 587
mol Pb (PO
3
4 )2
L
!
3 mol Pb2+
1 mol Pb (PO
3
4 )2
cPb2+ = 0.215 mol/L
cPO 3! = 0.071 587
mol Pb (PO
4
3
L
4 )2
"
2 mol PO 3!
4
1 mol Pb (PO
3
4 )2
cPO 3! = 0.143 mol/L
4
Statement: The amount concentration of lead ions in the solution is 0.215 mol/L and the amount concentration
of the phosphate ions is 0.143 mol/L.
Chapter 9 Questions, pages 159–160
1. a
2. False: Chemical contaminants form homogeneous mixtures with water.
3. In a formula equation, all of the compounds are represented by their chemical formulas.
4. No. Pb(OH)2 + 2 HCl → PbCl2 + 2 H2O
5. (a) CaCO3(aq) + BaCl2(aq) → CaCl2(aq) + BaCO3(s)
Total ionic equation: Ca2+(aq) + CO32–(aq) + Ba2+(aq) + 2 Cl–(aq) → Ca2+(aq) + 2 Cl–(aq) + BaCO3(s)
Net ionic equation: CO32–(aq) + Ba2+(aq) → BaCO3(s)
(b) The spectator ions in part (a) are Ca2+(aq) and 2 Cl– (aq).
6. The presence of some metal ions in solution can be identified by the colour of the precipitates that they
form.
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Chapter 9: Solutions and Their Reactions
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7. Answers may vary. Sample answer:
Table 1: Types of Contaminants
Contaminants
Source
physical
sand, clay, plastic products
biological
bacteria, natural water
organisms, waste material
chemical
industrial and chemical
contaminants
8. KCl(s) → K+(aq) + Cl–(aq)
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Effect
unpleasant smell and taste, area
water contamination
negative impact on aquatic systems,
hazardous to human health
high levels of mercury or other
harmful metals, brain damage
Chapter 9: Solutions and Their Reactions
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