Download Types of Chemical Reactions

Section 4
Chemical Reactions
1
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Ionic Theory of Solutions
• Many ionic compounds dissociate into
independent ions when dissolved in water
H 2O


NaCl(s )  Na (aq)  Cl (aq)
• These compounds that “freely” dissociate into
independent ions in aqueous solution are called
electrolytes.
• Their aqueous solutions are capable of conducting an
electric current.
2
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Ionic Theory of Solutions
• Not all electrolytes are ionic compounds.
Some molecular compounds dissociate into
ions.


HCl(aq)  H (aq)  Cl (aq)
• The resulting solution is electrically conducting,
and so we say that the molecular substance is an
electrolyte.
3
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Ionic Theory of Solutions
• Most molecular compounds (except acids)
dissolve but do not dissociate into ions.
C6 H12O6 (s) (glucose)  C6 H12O6 (aq)
H 2O
– These compounds are referred to as
nonelectrolytes. They dissolve in water to give a
nonconducting solution.
4
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Ionic Theory of Solutions
• Strong and weak electrolytes.
– A strong electrolyte is an electrolyte that exists in
solution almost entirely as ions.


NaCl(s)  Na (aq)  Cl (aq)
H 2O
Most ionic solids that dissolve in water do so
almost completely as ions, so they are strong
electrolytes.
strong electrolytes – strong acids, strong bases,
soluble salts
5
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Ionic Theory of Solutions
– A weak electrolyte is an electrolyte that dissolves
in water to give a relatively small percentage of
ions.
HCN (aq)  H 2O (l)


H 3O (aq)  CN (aq)
• Most soluble molecular compounds are either
nonelectrolytes or weak electrolytes.
•Weak electrolytes - weak acids, weak bases,
insoluble salts
Solutions of weak electrolytes contain only a small
percentage of ions. We denote this situation by writing the
equation with a double arrow.
6
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Solubility Rules for Ionic Compounds (Dissociates 100%)
1.) All compounds containing alkali metal cations and the ammonium ion
are soluble.
2.) All compounds containing NO3-, ClO4-, ClO3-, and C2H3O2- anions are
soluble.
3.) All chlorides, bromides, and iodides are soluble except those
containing Ag+, Pb2+, or Hg22+.
4.) All sulfates are soluble except those containing Hg22+, Pb2+, Ba2+, Sr2+,
or Ca2+. Ag2SO4 is slightly soluble.
5.) All hydroxides are insoluble except compounds of the alkali metals and
Ca2+, Sr2+, and Ba2+ are slightly soluble.
6.) All other compounds containing PO43-, S2-, CO32-, CrO42-, SO32- and
most other anions are insoluble except those that also contain alkali
metals or NH4+.
Generally, compound dissolves
> 0.10 M - soluble (aq)
< 0.01 M - insoluble (s)
in between - slightly soluble
(this class we will assume slightly soluble as soluble)
HW 26
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
7
Strong Acids (Ionizes 100%)
HCl, HBr, HI, HClO4, HNO3, H2SO4
Strong Bases (Dissociates 100%)
NaOH, KOH, LiOH, Ba(OH)2, Ca(OH)2, Sr(OH)2
8
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Molecular and Ionic Equations
• A molecular/formula unit equation is one in which the reactants and
products are written as if they were molecules/formula units, even
though they may actually exist in solution as ions.
Calcium hydroxide + sodium carbonate
F.U.
9
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Molecular and Ionic Equations
• An total ionic equation, however, represents strong
electrolytes as separate independent ions. This is a more
accurate representation of the way electrolytes behave in
solution.
– A complete ionic equation is a chemical equation in which strong
electrolytes (such as soluble ionic compounds, strong acids/bases) are
written as separate ions in solution . (note: g, l, insoluble salts (s), weak
acid/bases do not break up into ions)
F.U.
Ca(OH)2 (aq) +
Na2CO3 (aq)  CaCO3 (s) + 2 NaOH (aq)
Total ionic
10
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
• Net ionic equations.
– A net ionic equation is a chemical equation from
which the spectator ions have been removed.
– A spectator ion is an ion in an ionic equation that
does not take part in the reaction.
F.U.
Ca(OH)2 (aq) +
Na2CO3 (aq)  CaCO3 (s) + 2 NaOH (aq)
Total Ionic
Ca2+ (aq) + 2OH- (aq) + 2Na+ (aq) + CO32- (aq)  CaCO3 (s) + 2Na+ (aq) + 2OH- (aq)
Net
11
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Molecular and Ionic Equations
• Complete and net ionic equations
– Let’s try an example. First, we start with a
molecular equation.
F.U.
HNO3 (aq) + Mg(OH)2 (s) 
Total ionic
Net
12
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Ions in Aqueous Solution
Molecular and Ionic Equations
F.U.
HCN (aq) + NaOH (aq) 
Total ionic
Net
13
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
• Most of the reactions we will study fall into
one of the following categories
– Precipitation Reactions
– Acid-Base Reactions
– Oxidation-Reduction Reactions
14
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Precipitation Reactions
• A precipitation reaction occurs in aqueous
solution because one product is insoluble.
– A precipitate is an insoluble solid compound
formed during a chemical reaction in solution.
– For example, the reaction of sodium chloride with
silver nitrate forms AgCl(s), an insoluble precipitate.
NaCl(aq )  AgNO3 (aq )  AgCl(s)   NaNO3 (aq )
15
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Precipitation Reactions
• Precipitation Reactions.
– Suppose you mix together solutions of nickel(II)
chloride, NiCl2, and sodium phosphate, Na3PO4.
NiCl 2  Na3 PO 4 
16
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
F.U.
NaCl (aq) + Fe(NO3)2 (aq) 
HW 27
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
17
Types of Chemical Reactions
• Acid-Base Reactions
– Acids and bases are some of the most important
electrolytes.
– They can cause color changes in certain dyes
called acid-base indicators.
– Household acids and bases.
– Red cabbage juice as an acid-base indicator.
18
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Arrhenius Concept
– The Arrhenius concept defines acids as
substances that produce hydrogen ions, H+,
when dissolved in water.
– An example is nitric acid, HNO3, a molecular
substance that dissolves in water to give H+ and
NO3-.


HNO 3 (aq ) 
 H (aq )  NO 3 (aq )
H 2O
19
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Arrhenius Concept
– The Arrhenius concept defines bases as
substances that produce hydroxide ions, OH-,
when dissolved in water.
– An example is sodium hydroxide, NaOH, an ionic
substance that dissolves in water to give sodium
ions and hydroxide ions.


NaOH(s) 
 Na (aq)  OH (aq)
H 2O
20
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• By Arrhenius concept is ammonia an acid or
base?




NH 3 (aq )  H 2O(l )  NH 4 (aq )  OH (aq )
21
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Brønsted-Lowry Concept
– The Brønsted-Lowry concept of acids and bases
involves the transfer of a proton (H+) from the acid
to the base.
– In this view, acid-base reactions are protontransfer reactions.
22
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Brønsted-Lowry Concept
– The Brønsted-Lowry concept defines an acid as
the species (molecule or ion) that donates a
proton (H+) to another species in a protontransfer reaction.
– A base is defined as the species (molecule or
ion) that accepts the proton (H+) in a protontransfer reaction.
23
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Brønsted-Lowry Concept



NH 3 (aq )  H 2O(l )  NH 4 (aq )  OH (aq )
H+
the H2O molecule is the acid because it donates a
proton. The NH3 molecule is a base, because it accepts
a proton.
24
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• The Brønsted-Lowry Concept


HNO 3 (aq )  H 2O(l )  NO 3 (aq )  H 3O (aq )
H+
where HNO3 is an acid (proton donor) and H2O is a
base (proton acceptor).
Conjugate acid/base pairs – differ by a proton
25
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• In summary,
– The Arrhenius concept
acid: proton (H+) producer
base: hydroxide ion (OH-) producer
– The Brønsted-Lowry concept
acid: proton (H+) donor
base: proton (H+) acceptor
HW 28
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
26
Types of Chemical Reactions
Acid-Base Reactions
• Strong and Weak Acids and Bases
– A strong acid is an acid that ionizes completely
in water; it is a strong electrolyte.


HNO 3 (aq )  H 2O(l )  NO 3 (aq )  H 3O (aq )


HCl (aq )  H 2O(l )  Cl (aq )  H 3O (aq )
27
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• Strong and Weak Acids and Bases
– A weak acid is an acid that only partially ionizes
in water; it is a weak electrolyte.



HCN(aq)  H 2O(l )  CN (aq)  H 3O (aq)
28
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• Strong and Weak Acids and Bases
– A strong base is a base that is present entirely
as ions, one of which is OH-; it is a strong
electrolyte.
H O
2


NaOH(s)  Na (aq)  OH (aq)
29
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• Strong and Weak Acids and Bases
– A weak base is a base that is only partially
ionized in water; it is a weak electrolyte.



NH 3 (aq )  H 2O(l )  NH 4 (aq )  OH (aq )
30
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
• What are weak bases? NH3, NH2-, NH-, some anions.
• Which anions?
Salts may be acidic/basic/neutral and are composed of cations (positive
ions) and anions (negative ions)
cation anion
Acidic or neutral
Cations of strong bases
are neutral; otherwise
cation contributes acidity
basic or neutral
Anions of monoprotic strong
acids are neutral; otherwise
anion contributes basicity
i.e.
NaCN
NaCl
AlCl3
K2CO3
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
31
Types of Chemical Reactions
Acid-Base Reactions
• Neutralization Reactions
– One of the chemical properties of acids and bases is
that they neutralize one another.
– A neutralization reaction is a reaction of an acid
and a base that results in an ionic compound (salt)
and water.
A + B  salt + H2O
– The ionic compound that is the product of a
neutralization reaction is called a salt (acidic, basic,
or neutral).
HCN(aq)  KOH(aq)  KCN(aq)  H 2O(l )
acid
base
SA + WB 
SA + SB 
WA + SB 
salt
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
32
• Neutralization Reactions
– The net ionic equation for each acid-base
neutralization reaction involves a transfer of a
proton.
HCN(aq)  KOH(aq)  KCN(aq)  H 2O(l )
H+
See better in net eq.
Total:
Net:
33
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• Neutralization Reactions
– Consider the reaction of the strong acid , HCl(aq)
and a strong base, KOH(aq).
HCl(aq)  KOH(aq)  KCl(aq)  H 2O(l )
Total:
Net:
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
HW 29 &30
34
Types of Chemical Reactions
Acid-Base Reactions
• Acid-Base Reactions with Gas Formation
– Carbonates react with acids to form CO2, carbon
dioxide gas.
Na2CO3  2HCl  2NaCl  H 2O  CO2 
– Sulfites react with acids to form SO2, sulfur dioxide
gas.
Na2SO 3  2HCl  2NaCl  H 2O  SO 2 
– Sulfides react with acids to form H2S, hydrogen
sulfide gas.
Na 2S  2HCl  2NaCl  H 2S 
35
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Acid-Base Reactions
• Other Acid-Base reactions
Nonmetal oxides (or acid oxides or acid
anhydrides) react with water to form acids
SO2 + H2O  H2SO3
Metal oxides (or basic oxides or basic anhydrides)
react with water to form bases
Na2O + H2O  2NaOH
36
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
• Oxidation-Reduction Reactions (Redox rxn)
– Oxidation-reduction reactions involve the
transfer of electrons from one species to another.
– Oxidation is defined as the loss of electrons.
– Reduction is defined as the gain of electrons.
– Oxidation and reduction always occur
simultaneously.
37
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Redox reactions – transfer of ereduction – oxidation reactions
Reduction – gain of e- / gain of H / lost of O
Fe3+ + 1e-  Fe2+
(lower ox state)
note: must balance atoms and charges
38
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Oxidation - loss of e- / loss of H / gain of O
Fe2+
 Fe3+ + 1e-
(higher ox state)
H2O + BrO3-  BrO4- + 2H+ + 2e(Br oxidized: charge 5+  7+)
2H+ + 2e-  H2
(H reduced: charge 1+  0)
Oxidizing agent is species that undergoes reduction.
Reducing agent is species that undergoes oxidation.
Note: need both for reaction to happen; can’t have
something being reduced unless something else is being
oxidized.
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
39
Types of Chemical Reactions
• Oxidation-Reduction Reactions
Fe(s)  CuSO4 (aq)  FeSO4 (aq)  Cu(s)
40
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
• Oxidation-Reduction Reactions
Loss of 2 e-1 oxidation
2
2
Fe(s)  Cu (aq)  Fe (aq)  Cu(s)
Gain of 2 e-1 reduction
41
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Oxidation Numbers
– The concept of oxidation numbers is a simple way
of keeping track of electrons in a reaction.
– The oxidation number (or oxidation state) of an
atom in a substance is the actual charge of the
atom if it exists as a monatomic ion.
– Alternatively, it is hypothetical charge assigned
to the atom in the substance by simple rules.
42
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Oxidation Number Rules
Rule Applies to
Statement
1
Elements
The oxidation number of an atom in an element
is zero.
2
Monatomic ions
The oxidation number of an atom in a
monatomic ion equals the charge of the ion.
3
Oxygen
The oxidation number of oxygen is –2 in most of
its compounds. (An exception is O in H2O2 and
other peroxides, where the oxidation number is
–1.)
43
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Oxidation-Reduction Reactions
• Oxidation Number Rules
Rule Applies to
Statement
4
Hydrogen
The oxidation number of hydrogen is +1 in
most of its compounds.
5
Halogens
Fluorine is –1 in all its compounds. The other
halogens are –1 unless the other element is
another halogen or oxygen.
6
Compounds
and ions
The sum of the oxidation numbers of the
atoms in a compound is zero. The sum in a
polyatomic ion equals the charge on the ion.
HW 31
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
44
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Some Common Oxidation-Reduction
Reactions
– Most of the oxidation-reduction reactions fall into one of
the following simple categories:
– Combination Reaction
– Decomposition Reactions
– Displacement Reactions
– Combustion Reactions
45
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Combination Reactions
– A combination reaction is a reaction in which two
substances combine to form a third substance.
2 Sb (s)  3Cl2 (g)  2 SbCl3 (l)
46
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Decomposition Reactions
– A decomposition reaction is a reaction in which
a single compound reacts to give two or more
substances.
2 HgO (s)  2 Hg (l)  O2 (g)
47
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Displacement Reactions
– A displacement reaction (also called a singlereplacement reaction) is a reaction in which an
element reacts with a compound, displacing an
element from it.
Zn(s)  2HCl(aq)  ZnCl 2 (aq)  H 2 (g )
48
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Combustion Reactions
– A combustion reaction is a reaction in which a
substance reacts with oxygen, usually with the
rapid release of heat to produce a flame.
4 Fe (s) + 3 O2 (g)  2 Fe2O3 (s)
Common combustion reactions involve hydrocarbons
Hydrocarbon + O2  CO2 + H2O
HW 32
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
49
Types of Chemical Reactions
Oxidation-Reduction Reactions
• How do we balance Oxidation-Reduction
Reactions
– Look again at the net reaction of iron with
copper(II) sulfate.
2
2
Fe(s)  Cu (aq)  Fe (aq)  Cu(s)
– We can write this reaction in terms of two halfreactions.
50
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Types of Chemical Reactions
Oxidation-Reduction Reactions
• Describing Oxidation-Reduction Reactions
– A half-reaction is one of the two parts of an
oxidation-reduction reaction. One involves the loss
of electrons (oxidation) and the other involves the
gain of electrons (reduction).
2
Fe(s)  Fe (aq)
2
Cu (aq)  Cu(s)
oxidation half-reaction
reduction half-reaction
51
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Balancing Redox equations
- Must know charges (oxidation numbers) of species
including polyatomic ions
- Must know strong/weak acids and bases
- Must know the solubility rules
Oxidation Numbers – hypothetical charge assigned to the
atom in order to track electrons; determined by rules.
52
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
• Rules to balance redox
• 1.) Convert to net ionic form if equation is originally in molecular
form (eliminate spectator ions).
• 2.) Write half reactions.
• 3.) Balance atoms using H+ / OH- / H2O as needed:
– acidic: H+ / H2O put water on side that needs O or H (comes
from solvent)
– basic: OH- / H2O put water on side that needs H but if there is no
H involved then put OH- on the side that needs the O in a 2:1 ratio
2OH- / H2O balance O with OH, double OH, add 1/2 water to
other side.
4.) Balance charges for half rxn using e-.
5.) Balance transfer/accept number of electron in whole reaction.
6.) Convert equation back to molecular form if necessary (re-apply
53
Material was
developed by combining Janusa’s
material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
spectator
ions).
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
FU:
Zn(s) + AgNO3(aq)  Zn(NO3)2(aq) + Ag(s)
Total ionic:
Net ionic:
54
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Net:
Zn(s) + Ag+(aq)  Zn2+(aq) + Ag(s)
Ox:
Red:
Balanced net:
Balanced FU:
55
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Net:
MnO4-(aq) + Fe2+(aq)
H+
 Mn2+(aq) + Fe3+(aq)
Ox:
Red:
Balanced net:
56
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
FU:
KMnO4(aq) + NaNO2(aq) + HCl(aq)  NaNO3(aq) + MnCl2(aq) + KCl(aq) + H2O(l)
Net:
Ox:
Red:
Balanced net:
Balanced FU:
57
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
OH-
FU:
CrI3 (s) + Cl2 (g)  CrO42-(aq) + IO4-(aq) + Cl-(aq)
Ox:
Red:
Balanced net:
HW 33
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
58
Working with Solutions
• The majority of chemical reactions discussed
in general chemistry occur in aqueous
solution.
– When you run reactions in liquid solutions, it is
convenient to dispense the amounts of reactants
by measuring out volumes of reactant solutions.
59
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
• When we dissolve a substance in a liquid, we
call the substance the solute and the liquid
the solvent.
– The general term concentration refers to the
quantity of solute in a standard quantity of
solution.
60
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
• Molar concentration, or molarity (M), is
defined as the moles of solute dissolved in
one liter (cubic decimeter) of solution.
moles of solute
Molarity (M) 
liters of solution
61
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
A sample of NaNO3 weighing 0.38 g is placed in a
50.0 mL volumetric flask. The flask is filled with
H2O to the mark on the neck, dissolving the solid.
What is the molarity of the solution?
62
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
An experiment calls for the addition of 0.184 g
NaOH in an aqueous solution to reaction vessel.
How many milliliters of 0.150 M NaOH should be
added?
63
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
How many grams of NaCl should be put in a 50.0 mL
volumetric flask to give a 0.15 M NaCl solution
when the flask is filled to the mark with water?
HW 34
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
64
Working with Solutions
Molar Concentration
• The molarity of a solution and its volume are
inversely proportional. Therefore, adding
water makes the solution less concentrated.
– This inverse relationship takes the form of:
M i  Vi  M f  V f
Ci  Vi  C f  V f
65
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Working with Solutions
Molar Concentration
• Describe how you would make 100.0 mL of
1.00 M NH3 from a 14.8 M NH3 solution?
HW 35
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
66
Quantitative Analysis
• Analytical chemistry deals with the
determination of composition of materials-that
is, the analysis of materials.
– Quantitative analysis involves the determination
of the amount of a substance or species (analyte)
present in a material.
67
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Gravimetric Analysis
• Gravimetric analysis is a type of quantitative
analysis in which the amount of a species in a
material is determined by converting the
species into a product that can be isolated
and weighed.
– Precipitation reactions are often used in
gravimetric analysis.
– The precipitate from these reactions is then
filtered, dried, and weighed.
68
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Gravimetric Analysis
• Consider the problem of determining the
amount of lead in a sample of drinking water.
– Adding sodium sulfate (Na2SO4) to the sample will
precipitate lead(II) sulfate.
2

Na2SO4 (aq)  Pb (aq)  2Na (aq)  PbSO 4 (s)
– The PbSO4 can then be filtered, dried, and
weighed.
69
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Gravimetric Analysis
• Suppose a 1.00 L sample of polluted water was
analyzed for lead(II) ion, Pb2+, by adding an
excess of sodium sulfate to it. The mass of
lead(II) sulfate that precipitated was 229.8 mg.
What is the mass of lead (mg) in the sample?
Na2SO4 (aq)  Pb 2 (aq)  2Na (aq)  PbSO 4 (s)
70
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Volumetric Analysis
• An important method for determining the amount of a
particular substance is based on measuring the
volume of the reactant solution.
– Titration is a procedure for determining the
amount of unknown substance A by adding a
carefully measured volume of a solution with
known concentration of B until the reaction of A
and B is just complete.
– Volumetric analysis is a method of analysis
based on titration.
71
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Volumetric Analysis
• Consider the reaction of sulfuric acid, H2SO4,
with sodium hydroxide, NaOH:
– Suppose a beaker contains 35.0 mL of 0.175 M
H2SO4. How many milliliters of 0.250 M NaOH must
be added to completely react with the sulfuric acid?
72
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
Quantitative Analysis
Volumetric Analysis
– A flask contains a solution with an unknown amount of
HCl. This solution is titrated with 0.207 M NaOH. It
takes 4.47 mL of NaOH to complete the reaction.
What is the mass (g) of HCl in the sample?
HW 36
Material was developed by combining Janusa’s material with the lecture outline provided with Ebbing, D. D.; Gammon, S. D. General
Chemistry, 8th ed., Houghton Mifflin, New York, NY, 2005. Majority of figures/tables are from the Ebbing lecture outline.
73