Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.;
and Bruce E. Bursten
Chapter 4
Aqueous Reactions and
Solution Stoichiometry
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc.
Aqueous
Reactions
Solutions:
• Homogeneous
mixtures of two or
more pure
substances.
• The _____ is
present in greatest
abundance.
• All other substances
are _____.
Aqueous
Reactions
Dissociation
• When an ionic
substance dissolves
in water, the solvent
pulls the individual
ions from the crystal
and solvates them.
• This process is called
_____.
Aqueous
Reactions
Electrolytes
• Substances that
dissociate into ions
when dissolved in
water. Example:
• A _____ may dissolve
in water, but it does not
dissociate into ions
when it does so.
Example:
Aqueous
Reactions
Electrolytes and
Nonelectrolytes
_______________
_______________
tend to be
electrolytes.
Aqueous
Reactions
Electrolytes and
Nonelectrolytes
________________
tend to be
nonelectrolytes,
except for _____ and
_____.
Aqueous
Reactions
SAMPLE EXERCISE 4.1 Relating Relative Numbers of Anions and
Cations to Chemical Formulas
The diagram below represents an aqueous solution of one of the following
compounds: MgCl2 , KCl, or K2SO4. Which solution does it best represent?
Aqueous
Reactions
Electrolytes
• A strong electrolyte
dissociates
__________________
__________________
• A weak electrolyte
only dissociates
__________________
__________________
Aqueous
Reactions
Strong Electrolytes Are…
• Strong acids
• Strong bases
• Soluble ionic salts
Aqueous
Reactions
Precipitation Reactions
When one mixes ions
that form compounds
that are insoluble (as
could be predicted by
the solubility
guidelines), a
precipitate is formed.
Aqueous
Reactions
Metathesis (Exchange) Reactions
a.k.a. Double Replacement Rxns
• Metathesis comes from a Greek word that
means ______________
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
Aqueous
Reactions
Metathesis (Exchange) Reactions
• Metathesis comes from a Greek word that
means __________
• It appears the ions in the reactant
compounds __________________________
AgNO3 (aq) + KCl (aq) 
Aqueous
Reactions
AgNO3 (aq) + KCl (aq) 
How did we know that silver chloride was a solid???
We checked the ____________________.
Aqueous
Reactions
Aqueous
Reactions
Predict the products of the
following reactions
• BaCl2 (aq) + K2SO4 (aq)
• Fe2(SO4)3 (aq) + LiOH (aq)
• Mg(NO3)2 (aq) + CaS (aq)
• NaCl (aq) + KNO3 (aq)
Aqueous
Reactions
Solution Chemistry
• It is helpful to pay attention to exactly
what species are present in a reaction
mixture (i.e., solid, liquid, gas, aqueous
solution).
• If we are to understand reactivity, we
must be aware of just what is changing
during the course of a reaction.
Aqueous
Reactions
Molecular Equation
The _______________ equation lists the
reactants and products in their molecular
form.
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
Aqueous
Reactions
Ionic Equation
• In the ionic equation all __________________
(strong acids, strong bases, and soluble ionic salts)
are _______________ into their ___________.
• This _______________ reflects the species that are
found in the reaction mixture.
Ag+ (aq) + NO3- (aq) + K+ (aq) + Cl- (aq) 
AgCl (s) + K+ (aq) + NO3- (aq)
Aqueous
Reactions
Net Ionic Equation
• To form the _____ ionic equation, __________
anything that does not change from the left side of
the equation to the right.
Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) 
AgCl (s) + K+(aq) + NO3-(aq)
Aqueous
Reactions
Net Ionic Equation
• To form the net ionic equation, cross out anything
that does not change from the left side of the
equation to the right.
• The only things left in the equation are
_______________________ (i.e., react) during the
course of the reaction.
Ag+(aq) + Cl-(aq)  AgCl (s)
Aqueous
Reactions
Net Ionic Equation
• To form the net ionic equation, cross out anything
that does not change from the left side of the
equation to the right.
• The only things left in the equation are those things
that change (i.e., react) during the course of the
reaction.
• Those things that didn’t change (and were deleted
from the net ionic equation) are called ___________.
Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) 
AgCl (s) + K+(aq) + NO3-(aq)
Aqueous
Reactions
Writing Net Ionic Equations
1. Write a
2. Dissociate all
3. Cross out anything that remains
unchanged from the left side to the
right side of the equation.
4. Write the net ionic equation with the
species that remain.
Aqueous
Reactions
Writing Net Ionic Equations
Write the net ionic equation for each reaction
• Pb(NO3)2 (aq) + KI (aq)
• Li2S (aq) + BaBr2 (aq)
• NH4Cl (aq) + Sr(OH)2 (aq)
Aqueous
Reactions
Acids:
• Substances that
increase the
concentration of H+
when dissolved in
water (__________).
• Proton donors
(________________).
Aqueous
Reactions
Acids
There are only seven
strong acids:
•
•
•
•
•
•
•
Hydrochloric (HCl)
Hydrobromic (HBr)
Hydroiodic (HI)
Nitric (HNO3)
Sulfuric (H2SO4)
Chloric (HClO3)
Perchloric (HClO4)
Aqueous
Reactions
Bases:
• Substances that
increase the
concentration of
OH− when dissolved
in water (________).
• Proton acceptors
(______________).
Aqueous
Reactions
Bases
The strong bases
are the soluble salts
of hydroxide ion:
Aqueous
Reactions
Acid-Base Reactions
In an acid-base
reaction, _____
donates a proton
(H+) to the _____.
Aqueous
Reactions
Neutralization Reactions
Generally, when solutions of an acid and a base are
combined, the products are ____________________.
HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)
Aqueous
Reactions
Neutralization Reactions
When a strong acid reacts with a strong base, the net
ionic equation is…
HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)
H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) 
Na+ (aq) + Cl- (aq) + H2O (l)
Aqueous
Reactions
Neutralization Reactions
When a strong acid reacts with a strong base, the net
ionic equation is…
HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)
H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) 
Na+ (aq) + Cl- (aq) + H2O (l)
H+ (aq) + Cl- (aq) + Na+ (aq) + OH- (aq) 
Na+ (aq) + Cl- (aq) + H2O (l)
H+ (aq) + OH- (aq) → H2O (l)
Aqueous
Reactions
Neutralization Reactions
What does this have to do with you???
What happens when you have a stomach
ache?
What do you do about it?
Why?
Aqueous
Reactions
Neutralization Reactions
What does this have to do with you???
Many antacids contain magnesium hydroxide.
It undergoes a neutralization reaction with
stomach acid.
What acid constitutes the largest quantity of
stomach acid?
Write a net ionic equation for the neutralization
reaction between magnesium hydroxide and
hydrochloric acid.
Mg(OH)2 (s) + H+ (aq) → Mg2+ (aq) + H2O (l)
Aqueous
Reactions
Neutralization Reactions
Observe the
reaction between
Milk of Magnesia,
Mg(OH)2, and HCl.
Can you overdoes
on antacid?? What
do you think would
happen?
Aqueous
Reactions
Gas-Forming Reactions
• These metathesis reactions do not give the
_______________________.
• The __________________ decomposes to
give a gaseous product (
).
CaCO3 (s) + HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l)
NaHCO3 (aq) + HBr (aq) NaBr (aq) + CO2 (g) + H2O (l)
SrSO3 (s) + 2 HI (aq) SrI2 (aq) + SO2 (g) + H2O (l)
Aqueous
Reactions
Gas-Forming Reactions
• This reaction gives the predicted product, but
you had better carry it out in the hood, or you
will be very unpopular!
• Just as in the previous examples, a gas is
formed as a product of this reaction:
Na2S (aq) + H2SO4 (aq)  Na2SO4 (aq) + H2S (g)
Aqueous
Reactions
A Carbonated Beverage is
Another Example
How is a beverage carbonated?
What happens to the dissolved gas?
H2O (l) + CO2 (g) ↔ H2CO3 (aq)
H2O (l) + CO2 (g) ↔ 2H+ (aq) + CO3-2 (aq)
Aqueous
Reactions
Oxidation-Reduction Reactions
• An _______ occurs
when an atom or ion
loses electrons.
• A _______ occurs
when an atom or ion
gains electrons.
Aqueous
Reactions
Oxidation-Reduction Reactions
Aqueous
Reactions
Oxidation Numbers
To determine if an oxidation-reduction
reaction has occurred, we assign an
_________________ to each element
in a neutral compound or charged entity.
Aqueous
Reactions
Oxidation Numbers
• Elements in their elemental form have
an oxidation number of _____.
• The oxidation number of a monatomic
ion is ___________________.
Aqueous
Reactions
Oxidation Numbers
• Nonmetals tend to have negative
oxidation numbers,
________________________________
______________________________.
Oxygen has an oxidation number of −2,
except in the peroxide ion in which it has
an oxidation number of −1.
Hydrogen is −1 when bonded to a metal,
+1 when bonded to a nonmetal.
Aqueous
Reactions
Oxidation Numbers
• Nonmetals tend to have negative
oxidation numbers, although some are
positive in certain compounds or ions.
Fluorine always has an oxidation number
of −1.
The other halogens have an oxidation
number of −1 when they are negative; they
can have positive oxidation numbers,
Aqueous
however, most notably in oxyanions.
Reactions
Oxidation Numbers
• The sum of the oxidation numbers in a
neutral compound is 0.
• The sum of the oxidation numbers in a
polyatomic ion is the
_________________.
Aqueous
Reactions
Oxidation Numbers
Find the oxidation numbers for each of the
following species.
•
•
•
•
•
•
CO32H 2S
S8
SCl2
SO42Cr2O72Aqueous
Reactions
Displacement Reactions
• In displacement
reactions, ions
________________.
• The ions, then, are
reduced.
Aqueous
Reactions
Displacement Reactions
In this reaction,
silver ions ________
copper metal.
Cu (s) + 2 Ag+ (aq)  Cu2+ (aq) + 2 Ag (s)
Aqueous
Reactions
Displacement Reactions
The reverse reaction,
however, does not
occur.
x Cu (s) + 2 Ag+ (aq)
Cu2+ (aq) + 2 Ag (s) 
Aqueous
Reactions
Activity Series
Aqueous
Reactions
Use the Activity Series to predict the products of the
following reactions. If the reactions does take place,
write the net ionic equation for the reaction. Lastly,
identify the species being oxidized and reduced.
• Al (s) + HBr (aq)
• Fe(s) + KI (aq)
• Zn (s) + Ni(NO3)2 (aq)
Aqueous
Reactions
Molarity
• Two solutions can contain the same
compounds but be quite different because the
proportions of those compounds are different.
• Molarity is one way to measure the
__________________________________.
Aqueous
Reactions
Mixing a Solution
• How many grams of
silver nitrate are
required to make 100
mL of a 0.5 M solution?
• How many grams of
NaOH are required to
make 50 mL of an 8.2 M
solution?
Aqueous
Reactions
Dilution
Aqueous
Reactions
Dilution
• You have 1L of a 1.00 M stock solution
of hydrochloric acid. You need to make
500 mL of a 0.20M solution. How much
of the stock solution is needed?
• You need to make 100 mL of 0.50 M
nitric acid. The storage bottle reads
6.0M. How much of the 6.0M nitric acid
will you need?
Aqueous
Reactions
Using Molarities in
Stoichiometric Calculations
How many grams of Ca(OH)2 are needed
to neutralize 20.0 mL of a 0.150 M
H2SO4 solution?
Aqueous
Reactions
Using Molarities in
Stoichiometric Calculations
How many liters of 0.500 M HCl are
needed to react completely with 0.100
mol Pb(NO3)2, forming the precipitate
PbCl2?
Aqueous
Reactions
Titration
The _____________
technique in which
one can calculate
the
________________
________________
________________.
Aqueous
Reactions
Titration
Aqueous
Reactions
Titration Example
A 1.034-g sample of impure oxalic acid
(H2C2O4) is dissolved in water and an
acid-base indicator is added. The
sample required 34.47 mL of 0.485 M
NaOH to reach the equivalence point.
What is the mass of oxalic acid and
what is its mass percent in the sample?
Aqueous
Reactions
Titration
A 0.263-g sample of sodium carbonate, a
base, requires 28.35 mL of aqueous
HCl for titration to the equivalence point.
What is the molarity of the HCl?
Aqueous
Reactions