Objectives
Properties of acids and bases
The pH scale
Distinguish between strong and weak
acids and list the uses of these acids
Distinguish between strong and weak
bases and list the uses of these bases
Understand neutralization and
applications of neutralization
An acid (from the Latin acidus meaning
sour) is traditionally considered any
chemical compound that, when
dissolved in water, gives a solution
with a hydrogen ion activity greater
than in pure water, i.e. a pH less than
7.0.
In chemistry, a base is most commonly
thought of as an aqueous substance that
can accept hydrogen ions. Bases are
also the oxides or hydroxides of
metals.
Acids and Bases
When a substance dissolves in water it
makes a solution.
Solutions can be sorted by whether
they are: acid, basic (alkali) or
neutral.
Acids & Bases
Acids







Taste sour
Turns litmus red
Neutralizes bases
Acids are made of one
or more H+ ions and
one negative ion
Ex. HCl
Produces H+ ions
when dissolved in
water
Are corrosive
Bases








Taste bitter
Turns litmus blue
Neutralizes acids
Bases are made of
metals combined with
hydroxide ions (OH-)
Ex. NaOH
Produces OH- when
dissolved in water
Feel slippery or
“soapy”
Are corrosive
General properties
BASES
ACIDS
Taste bitter
Taste sour
Turn litmus
Turn litmus
React with active metals –Feel soapy or slippery
(react with fats to
Fe, Zn
make soap)
React with acids
React with bases
blue to red
red to blue
Definitions
Arrehenius
only in water
Bronsted-Lowry
any solvent
Acids – produce H+
Bases - produce OHAcids – donate H+
Bases – accept H+
Neutralization
In general: Acid + Base  Salt + Water
All neutralization reactions are double displacement reactions.
HCl + NaOH

NaCl + HOH
HCl + Mg(OH)2 
H2SO4 + NaHCO3 
Acids & Bases
STRONG
_ completely ionized
_ strong electrolyte
Strong Acids:
HClO4
H2SO4
HI
HBr
HCl
HNO3
vs
WEAK
_ partially ionized
_ weak electrolyte
Strong Bases:
LiOH
NaOH
KOH
Ca(OH)2
Sr(OH)2
Ba(OH)2
Examples
Strong Acids:
HClO4
H2SO4
HI
HBr
HCl
HNO3
Strong Bases:
LiOH
NaOH
KOH
Ca(OH)2
Sr(OH)2
Ba(OH)2
Let’s examine the behavior of
an acid, HA, in aqueous solution.
HA
What happens to the HA molecules in solution?
100% dissociation of HA
HA
H+
Strong Acid
AWould the
solution be
conductive?
Partial dissociation of HA
HA
H+
Weak Acid
AWould the
solution be
conductive?
Marieb, Fig 26.11
Strong and Weak Acids/Bases
Strong acids/bases – 100% dissociation into ions
HCl
HNO3
H2SO4
NaOH
KOH
Weak acids/bases – partial dissociation,
both ions and molecules
CH3COOH
NH3
acid rain (NOx, SOx)
pH of 4.2 - 4.4 in
Washington DC area
pH
0-14 scale for the chemists
2
3
4
5
acidic
(H+) > (OH-)
normal rain (CO2)
pH = 5.3 – 5.7
6
7
8
neutral @ 25oC
(H+) = (OH-)
distilled water
fish populations
drop off pH < 6
and to zero pH < 5
9
10
11
basic or alkaline
(H+) < (OH-)
natural
waters pH =
6.5 - 8.5
12
On the pH scale, values below 7 are acidic, a value of 7 is
neutral, and values above 7 are basic.
Marieb, 2.12
pH of Rainwater
across United States in 2001
You
are
here!
Why is the eastern US more acidic?
http://nadp.sws.uiuc.edu/isopleths
What is acid rain?
Dissolved carbon
dioxide
lowers the pH
CO2 (g) + H2O  H2CO3  H+ + HCO3-
Atmospheric pollutants from combustion
NO, NO2 + H2O …  HNO3
SO2, SO3 + H2O …  H2SO4
pH < 5.3
both
strong
acids
Vocabulary
Hydronium ion -is the common name for
the aqueous cation H3O+
Hydroxide ion – common name for the
aqueous anion OHIndicator –is a chemical compound that is
added in small amounts to a solution so
that the pH (acidity or basicity) of the
solution can be determined visually.
Buffers - make the pH of the solution
change very little when a small amount of
strong acid or base is added to it.
Vocabulary
Soaps -a cleansing agent created by the
chemical reaction of a fatty acid with an alkali
metal hydroxide. (KOH)
Detergents -developed in response to the
shortage of the animal and vegetable fats used
to make soap during World War I and World War
II. Detergents are primarily surfactants, which
could be produced easily from petrochemicals.
Titration -one solution (solution #1) is added to
another solution (solution #2) until a chemical
reaction between the components in the
solutions has run to completion.
1.
2.
3.
4.
5.
6.
7.
8.
What does pH stand for?
Define acid.
Define base.
List the properties of acids
List the properties of bases
Define indicator
Define soap (how are they made)
What do we mean by neutralization
pH Calculations
pH
pH = -log[H+]
[H+]
[H+] = 10-pH
[H+] [OH-] = 1.0 x10-14
pH + pOH = 14
pOH
pOH = -log[OH-]
[OH-]
[OH-] = 10-pOH
pH and pOH calculations
1.
What is the pOH of a solution whose pH is 3.45?
2. What is the [OH-] of a solution whose pOH = 2.86 ?
3. The pH of a softdrink is determined to be 4.0. What is
the [OH-] of the drink?
4. What is the pOH of a solution whose [H+] is 2.75 x 10-4 M?
5. What is the [H+] of a solution whose pOH = 2.86 ?
6. What is the pH of a solution whose pOH is 11.09?
7. What is the [H+] of an acid solution that has a
pH of 3?