Chapter 4: Aqueous Rxns
and Solution Stoichiometry
Recommended Text
Problems
„
1, 3, 7, 13, 19, 21, 25, 31, 37, 39ac,
„
41b, 45, 49, 51, 55abe, 59, 63, 65b, 71,
„
75, 79abc, 81, 85, 90, 92, 103, 107
Schedule
04 27
Chapter 4: Aqueous
Reactions and Solution
Stoichiometry
5. Solubility Rules, Types of
Reactions and N.I.
Equations Data Collection
04 29
Chapter 4: Aqueous
Reactions and Solution
Stoichiometry
5. Solubility Rules, Types of
Reactions and N.I.
Equations Data Analysis
05 04
Chapter 4: Aqueous
Reactions and Solution
Stoichiometry
6. Standardization of a NaOH
Solution
05 06
Chapter 5:
Thermochemistry
7. Molar Mass of an
Unknown Solid Acid
(LQ02)
4
5
Solutions
„
Definition:
„
Components
„
The solvent
„
The solutes
Dissociation
„
Definition
„
Animation
Electrolytes
„
An electrolyte is a substances that
„
A strong electrolyte
„
A weak electrolyte
Strong Electrolytes
„
Strong acids
„
Strong bases
„
„
Hydroxide
Soluble ionic salts
Electrolytes
„
A nonelectrolyte may dissolve in water,
but it does not dissociate into ions
when it does so.
Electrolytes and
Nonelectrolytes
Chemical Reactions
„
After mixing chemicals together, how
do you know reactions occurred
Precipitation Reactions
Solution Chemistry
„
How can we predict what reactions
occur in a reaction mixture?
Equations
„
The molecular equation
„
The (total, complete) ionic equation
„
The net ionic equation,
Writing Net Ionic Equations
1.
2.
3.
4.
Write a balanced molecular equation.
Dissociate all strong electrolytes.
Cross out anything that remains unchanged from
the left side to the right side of the equation.
Write the net ionic equation with the species that
remain.
CaCO3(s) + HCl → ?
„
Molecular Equation:
Total Ionic Equation:
„
Net Ionic Equation:
„
Writing Net Ionic Equations
„
K3PO4(aq) + 3HNO3(aq) → ?
„
KNO3(aq) + HCl(aq) → ?
Metathesis (Exchange)
Reactions
„
„
Metathesis comes from a Greek word
that means “to transpose.”
It appears the ions in the reactant
compounds exchange, or transpose,
ions.
Equations
AgNO3 (aq) + KCl (aq) ⎯→
Acid-Base Reactions
„
Characteristics
„
Acid
„
Base
Arrhenius Concept of Acids
and Bases
„
Acid
„
Base
Arrhenius Concept of Acids
and Bases
„
Strong acid
„
A substance
„
There are only seven strong acids:
Arrhenius Concept of Acids
and Bases
„
Strong base
„
„
A substance
The strong bases are the soluble metal
salts of hydroxide ion:
Arrhenius Concept of Acids
and Bases
„
Most other acids and bases are weak.
„
They are
„
An example is acetic acid, HC2H3O2.
„
Ammonium hydroxide, NH4OH, is a weak
base.
Arrhenius Concept of Acids
and Bases
„
Strong base
„
„
A substance ionizes completely in aqueous
solution to give OH-(aq) and a cation.
The strong bases are the soluble metal salts of
hydroxide ion:
„
„
„
„
Alkali metals
Calcium
Strontium
Barium
Arrhenius Concept of Acids
and Bases
„
Polyprotic Acid
„
Example:
Arrhenius Concept of Acids
and Bases
„
Ammonia, NH3??
Neutralization Reactions
„
Generally, when solutions of an acid
and a base are combined,
„
the products are a salt and water.
CH3COOH
+ NaOH (aq)
⎯→CH3COONa
(aq)
(aq)
+ H2O
(l)
Neutralization Reactions
„
Net ionic reaction
„
„
„
„
Strong acid + Strong base
Strong acid + Weak base
Weak acid + Strong base
Weak acid + Weak base
Brønsted-Lowry Concept of
Acids and Bases
„
Acid
„
Base
Brønsted-Lowry Concept of
Acids and Bases
„
Conjugate acid-base pair
Example:
Gas-Forming Reactions
„
Some metathesis reactions do not give the
product expected.
„
When a
„
„
the products are a salt, carbon dioxide, and water.
When a
„
The products are a salt, sulfur dioxide, and water.
Oxidation-Reduction Reactions
„
An oxidation occurs
„
A reduction occurs
„
One cannot occur
without the other.
Oxidation Numbers
„
„
„
„
Elements in their elemental form have an oxidation
number of 0.
The oxidation number of a monatomic ion is the
same as its charge.
The sum of the oxidation numbers in a neutral
compound is 0.
The sum of the oxidation numbers in a polyatomic
ion is the charge on the ion.
Oxidation Numbers
„
Nonmetals tend to have negative
oxidation numbers, although some are
positive in certain compounds or ions.
Displacement Reactions
„
In displacement reactions,
„
For example:
„
silver ions oxidize copper metal.
Cu (s) + 2 Ag+ (aq) ⎯→ Cu2+ (aq) + 2 Ag (s)
„
The reverse reaction, however, does not occur.
Cu2+ (aq) + 2 Ag (s) ⎯→ Cu (s) + 2 Ag+ (aq)
x
Activity Series
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
concentration of a solution.
Example
„
Calculate the molarity of a solution made by
dissolving 23.4 g of sodium sulfate (Na2SO4)
in enough water to form 125 mL of solution.
Practice
„
Calculate the molarity of a solution made by
dissolving 5.00 g of glucose (C6H12O6) in
sufficient water to form exactly 100 mL of
solution.
Example
„
What are the molar concentrations of
each of the ions present in a 0.025 M
aqueous solution of calcium nitrate?
Practice
„
(a) How many grams of Na2SO4 are there in
15 mL of 0.50 M Na2SO4? (b) How many
milliliters of 0.50 M Na2SO4 solution are
needed to provide 0.038 mol of this salt?
To Prepare a Solution with
Known Concentration
„
To prepare a solution of a
known molarity,
Dilution
Example
„
How many milliliters of 3.0 M H2SO4 are
needed to make 450 mL of 0.10 M H2SO4?
Practice
(a) What volume of 2.50 M lead(II) nitrate solution
contains 0.0500 mol of Pb2+?
(b) How many milliliters of 5.0 M K2Cr2O7 solution must
be diluted to prepare 250 mL of 0.10 M solution?
(c) If 10.0 mL of a 10.0 M stock solution of NaOH is
diluted to 250 mL, what is the concentration of the
resulting stock solution?
Using Molarities in
Stoichiometric Calculations
Example
How many grams of Ca(OH)2 are needed to
neutralize 25.0 mL of 0.100 M HNO3?
Practice
a) How many grams of NaOH are needed to neutralize
20.0 mL of 0.150 M H2SO4 solution?
b) How many liters of 0.500 M HCl(aq) are needed to
react completely with 0.100 mol of Pb(NO3)2(aq),
forming a precipitate of PbCl2(s)?
Titration
Titration
Example
How many grams of Ca(OH)2 are needed to
neutralize 25.0 mL of 0.100 M HNO3?
Practice
a) How many grams of NaOH are needed to neutralize
20.0 mL of 0.150 M H2SO4 solution?
b) How many liters of 0.500 M HCl(aq) are needed to
react completely with 0.100 mol of Pb(NO3)2(aq),
forming a precipitate of PbCl2(s)?
Vocabulary/Terminology
„
„
„
„
Electrolyte
Arrhenius
Acids/Bases
Brønsted-Lowry Acids
and Bases
Metathesis
(Exchange) Reactions
„
Double replacement
reaction
„
„
„
„
„
„
Displacement
Reactions
Neutralization
Reactions
Oxidation/
Reduction
Dilution
Titration
Standardization