Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
1
Reactions
Chapter 4
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
2
Aqueous Solutions
Water is the dissolving medium, or solvent.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
3
Figure 4.1 The Water Molecule is Polar
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
4
Some Properties of Water
Water is “bent” or V-shaped. The O-H bonds are covalent. Water is a polar molecule. Hydration occurs when salts dissolve in
water.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
5
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
6
• http://mathinscience.info/teach/k5_science/chemistry/mastering_matter/matter_animations/salt_cystl_watr_mol_web.swf
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
7
Figure 4.2Polar Water Molecules Interact with the Positive and Negative Ions of a
Salt
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
9
A Solute
dissolves in water (or other “solvent”)
changes phase (if different from the solvent)
is present in lesser amount (if the same phase as the solvent)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
10
A Solvent
retains its phase (if different from the solute)
is present in greater amount (if the same phase as the solute)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
11
Electrolytes
Strong - conduct current efficiently
NaCl, HNO3
Weak - conduct only a small current
vinegar, tap water
Non - no current flows
pure water, sugar solution
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
12
Figure 4.5BaCI2 Dissolving
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
13
Acids
Strong acids - dissociate completely to produce H+ in solution
hydrochloric and sulfuric acid
Weak acids - dissociate to a slight extent to give H+ in solution
acetic and formic acid
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
14
Figure 4.6HCI (aq) is Completely Ionized
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
15
Figure 4.8Acetic Acid in Water
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
16
Bases
Strong bases - react completely with water to give OH ions.
sodium hydroxide
Weak bases - react only slightly with water to give OH ions.
ammonia
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
20
Types of Double Displacement Reactions
Precipitation reactionsAgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
Acid-base reactionsNaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
Oxidation-reduction reactionsFe2O3(s) + Al(s) Fe(l) + Al2O3(s)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
21
Simple Rules for Solubility
1. Most nitrate (NO3) salts are soluble.
2. Most alkali (group 1A) salts and NH4+ are soluble.
3. Most Cl, Br, and I salts are soluble (NOT Ag+, Pb2+, Hg22+)
4. Most sulfate salts are soluble (NOT BaSO4, PbSO4, HgSO4, CaSO4)
5. Most OH salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble)
6. Most S2, CO32, CrO4
2, PO43 salts are only slightly soluble.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
22
Describing Reactions in Solution
1. Molecular equation (reactants and products as compounds)
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
2. Complete ionic equation (all strong electrolytes shown as ions)
Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq)
AgCl(s) + Na+(aq) + NO3(aq)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
23
Describing Reactions in Solution (continued)
3. Net ionic equation (show only components that actually react)
Ag+(aq) + Cl(aq) AgCl(s)
Na+ and NO3 are spectator ions.
Quick Review – Are you Ready?
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
24
47%
53% 1. Yes
2. No
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
When Fe(NO3)2 dissolves in water, what particles are present in the solution?
0%
6%
88%
6% 1. Fe+ and (NO3)2–
2. Fe2+ and 2 NO3–
3. Fe and 2 NO3
4. Fe and N2 and 3 O2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Pb(NO3)2 + 2 KI PbI2 + 2 KNO3
What is the observable evidence that the above reaction occurs?
88%
0%
0%
12% 1. An explosion.
2. A gas forms.
3. The solution boils.
4. A solid forms.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
When an acid and a base react to form a salt and water, the reaction is called a(n):
0%
100%
0%
0% 1. cancellation.
2. elimination.
3. neutralization.
4. adduct formation.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Which mixture will produce a precipitate?
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
28
1. NH3 + HF
2. HClO4 + KOH
3. Na2SO4 + PbCl24. Ca(NO3)2 + KC2H3O2
5. (NH4)2CO3 + Na3PO4
12%
24%
47%
18% 0%
1. 2 3 4 5
1. 1.
2. 2
3. 3
4. 4
5. 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is(are) the spectator ion(s) in the following reaction?
KOH (aq) + HF (aq) KF (aq) + H2O (l)
0%
6%
82%
6%
6% 1. K+
2. F–
3. K+ and F–
4. OH– and H+
5. OH–
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Which of the following reactions has the net ionic equation:
H+ (aq) + OH– (aq) H2O (l)
1) HClO4 + KOH
2) HF + NaOH
3) H3PO4 + KOH
4) H2SO4 + Ca(OH)2
53%
0%
0%
41%
6% 1. Reaction 1
2. Reactions 1, 4
3. Reactions 2, 3
4. Reactions 2, 4
5. Reactions 3, 4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
31
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
32
Other Reactions
• Single displacement
• Combustion
• Synthesis
• Decomposition
All of these involve a transfer of electrons and are oxidation-reduction (Redox) reactions
© 2009, Prentice-Hall, Inc.
Oxidation-Reduction Reactions
• An oxidation occurs when an atom or ion loses electrons.
• A reduction occurs when an atom or ion gains electrons.
• One cannot occur without the other.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
34
Rules for Assigning Oxidation States
1. Oxidation state of an atom in an element = 0
2. Oxidation state of monatomic ion = charge
3. Oxygen = 2 in covalent compounds (except in peroxides where it = 1)
4. H = +1 when bonded to nonmetal; -1 when bonded to metal
5. Fluorine = 1 in compoundsThe other halogens have an oxidation number of −1
when they are negative; they can have positive oxidation numbers, however, most notably in oxyanions (polyatomic ions with oxygen)
6. Sum of oxidation states = 0 in compounds Sum of oxidation states = charge of the ion
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
35
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
36
Redox Reactions - Terms
• Oxidation – loss of electrons (increase in oxidation number)
• Reduction – gain of electrons (decrease in oxidation number)
• Oxidizing agent – the compound that is the electron acceptor
• Reducing agent – the compound that is the electron donor
When an atom undergoes reduction, it _______ electrons.
0%
0%
6%
94% 1. gains
2. loses
3. retains
4. balances
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of sulfur in the following compound?
SO2
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
38
6%
0%
94%
0% 1. -4
2. +4
3. -2
4. +2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of oxygen in the following compound?
MgO
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
39
12%
88%
0%
0% 1. -4
2. +4
3. -2
4. +2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of Manganese in the following compound?
MnO2
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
40
6%
0%
94%
0% 1. -4
2. +4
3. -2
4. +2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of Fluorine in the following compound?
F2
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
41
18%
41%
6%
35% 1. -1
2. +1
3. 0
4. -2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of Sulfur in the following compound?
SO42-
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
42
6%
6%
82%
6% 1. +8
2. +6
3. -2
4. +4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of manganese in the permanganate ion?
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
43
59%
0%
29%
12% 1. +8
2. +6
3. -6
4. +7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is the oxidation number of nitrogen in the nitrite ion?
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
44
24%
0%
12%
65% 1. +3
2. +5
3. -5
4. +2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is reduced in the following equation?
Al + Cu(NO3)2 Cu + Al(NO3)3
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
45
0%
0%
89%
11% 1. Al
2. Cu
3. Cu(NO3)2
4. Al(NO3)3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
What is oxidized in the following equation?
Al + Cu(NO3)2 Cu + Al(NO3)3
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
46
25%
25%
25%
25% 1. Al
2. Cu
3. Cu(NO3)2
4. Al(NO3)3
What is reducing agent in the following equation?
Al + Cu(NO3)2 Cu + Al(NO3)3
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
47
25%
25%
25%
25% 1. Al
2. Cu
3. Cu(NO3)2
4. Al(NO3)3
What is oxidizing agent in the following equation?
Al + Cu(NO3)2 Cu + Al(NO3)3
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
48
25%
25%
25%
25% 1. Al
2. Cu
3. Cu(NO3)2
4. Al(NO3)3
Which substance is serving as the reducing agent in the following reaction?
14H+ + Cr2O72- + 3Ni 3Ni2+ + 2Cr3+ + 7H2O
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
49
20%
20%
20%
20%
20% A. H2O
B. H+
C. Ni2+
D. Ni
E. Cr2O72-
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
50
Balancing by Half-Reaction Method
1. Write separate reduction, oxidation reactions.
2. For each half-reaction:
Balance elements (except H, O)
Balance O using H2O
Balance H using H+
Balance charge using electrons
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
51
Balancing by Half-Reaction Method (continued)
3. If necessary, multiply by integer to equalize electron count.
4. Add half-reactions.
5. Check that elements and charges are balanced.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
52
Half-Reaction Method - Balancing in Base
1. Balance as in acid.
2. Add OH that equals H+ ions (both sides!)
3. Form water by combining H+, OH.
4. Check elements and charges for balance.