Chemistry 1
Chapter 18
Acids and Bases
Chapter 18 Objectives
I. Compare and Contrast the Bronsted-Lowry and Arrhenias definitions of
acids and bases.
II. Use the proton donor/acceptor concept to identify conjugate acid base
pairs.
III. Identify the common physical and chemical properties of acids and
bases and know how indicators are used to identify them.
IV. Write the expression for the acid/base dissociation constant and use
the data to calculate the dissipation constant.
V. Explain how the dissociation constant can be used to compare the
relative strengths of acids and bases.
VI. Describe a salt hydrolysis reaction and identify the result as acidic
basic or neutral.
VII. Know types of acids and bases, be able to name them using correct
nomenclature.
Arrhenius
Substances that dissociate in
water to make H+ or (H3O+) ions.
Bronsted-Lowry
Proton Donor
Lots of ions
Few Molecules
Facts:
1. Acids are strong when they dissociate in
water (most of the acid breaks up)
2. Acids are weak when they DON’T
dissociate in water (only small amounts of
the acid actually breaks up)
3. The stronger the acid, the weaker the
conjugate base.
4. The weaker the acid, the stronger the
conjugate base.
Arrhenius
Substances that dissociate in
water to make OH- ions
Bronsted-Lowry
Proton Acceptor
FOUR STRONG BASES
Calcium Oxide (CaO)
Sodium Hydroxide (NaOH)
Potassium Hydroxide (KOH)
Calcium Hydroxide(Ca(OH)2)
A strong base is a base which hydrolyzes completely, raising the pH of
the solution towards 14
Acid Vs. Base
Acids
Bases
Dissolve Metals
Dissolve Organics
Taste Sour or Tart (in Soda)
Taste Bitter
Neutralize Bases
Neutralize Acids
Litmus
Litmus
Red
Blue
Together acids and bases for neutralization reactions
The strength of an acid is
measured by it’s acid
dissociation constant (Ka)
The pH of a solution is a measurement
of the concentration of hydronium.
This will depend on the concentration
and nature of acids and bases in
solution.
Scale on next
slide
B
A
B + H2O
A
B
HB+ + OH-
Acidic
pH
Basic
Neutral
Examples
0
Battery acid / STRONG hydrochloric acid
1
Hydrochloric acid secreted by stomach lining
2
Lemon Juice / Gastric Acid / Vinegar
3
Grapefruit / Orange Juice / Soda
4
Acid Rain / Tomato Juice
5
Soft drinking water / Black Coffee
6
Saliva / Urine
7
"Pure" water
8
Sea water
9
Baking Soda
10
Milk of Magnesia / Great Salt Lake
11
Ammonia solution
12
Soapy water
13
Bleaches / Oven Cleaner
14
Liquid drain cleaner
Naming Acids
The name of the Acid typically
comes from the anion it
produces when it dissociates.
Three Rules for naming Acids
If the anion ends in -ide, the name of the acid
that produces it includes the name of the anion…
hydro___ic acid
If the anion has no prefix and ends in -ate, the
name of the acid that produces this ion ends in ic… ___ ic acid
If the anion ends in -ite, the acid that produces it
has no prefix and ends in -ous… ___ ous acid
The Acid Dissociation Constant
The acid dissociation
constant, Ka is a measure of
the strength of an acid.
Call a weak acid HA, H is a Hydrogen molecule
and A is the rest of the acid molecule. Because HA
is weak it only partially dissociates in water.
HA (aq) + H2O (l)
Equilibrium constant is = to Keq
Keq =
[H3O+][A-]
[HA][H2O]
H3O+ (aq) +A- (aq)
The Acid Dissociation Constant
Keq =
[H3O+][A-]
[HA][H2O]
Keq [H2O] =
[H3O+][A-]
[HA][H2O]
Keq and [H2O] equals a constant,
which is called the acid
dissociation constant or Ka
Ka =
[H3O+][A-]
[HA]
It is possible to predict whether a salt hydrolysis
reaction produces an acidic solution or basic solution.
There are four possibilities for salts
Strong Acid + Strong Base
Neutral
Strong Acid + Weak Base
Slightly Acidic
Weak Acid + Strong Base
Slightly Basic
Weak Acid + Weak Base
Acidic / Basic / Neutral
According to
Arrhenius, Acids are:
A) Substances that dissociate
in water to make OH- ions
B) Substances that dissociate
in water to make H+ or (H3O+)
ions.
C) Proton Donors
D) Proton Acceptors
Identify the conjugate
pairs:
A
B
HA +H2O
A
B
H3 O+ + A
Bases are:
A) Caustic
B) Corrosive
The acid dissociation
constant that measures
the strength of an acid is
represented by:
A) Keq
B) Ksp
C) Ka
D Kb
If the acid in a salt is
stronger than the base
then the salt is:
A) Highly Basic
B) Highly Acidic
C) Neutral
D) Slightly Acidic
If naming an acid with a
Hydrogen and a nitrate
(NO3-) ion, what would
you call it?
A) Nitrous Acid
B) Nitric Acid
C) Hydronitric Acid