Chapter 19
Acids and Bases
TEKS
(G) define acids and bases and distinguish
between Arrhenius and Bronsted-Lowry
definitions and predict products in acid base
reactions that form water;
 (H) understand and differentiate among acidbase reactions, precipitation reactions, and
oxidation-reduction reactions;
 (I) define pH and use the hydrogen or hydroxide
ion concentrations to calculate the pH of a
solution; and

Properties of Acids and Bases
Acids

Tastes sour
reacts with metals to
produce hydrogen gas
 Reacts with carbonates
to produce carbon dioxide
 conducts electricity so
are good electrolytes
 Turns blue litmus red
 Has a pH between 0-6
 Reacts with a base to
produce salt and water

Bases






Tastes bitter
Slippery
conducts electricity
Turns red litmus blue
Reacts with an acid to
produce salt and
water
Has a pH above 7
Ions in Solution
Acidic Solution
Neutral
solutions
Basic Solution
• contains • neither
• contains
more H+
acidic or
more OHions than
basic
ions than
OH- ions • equal #
H+ ions
• H+ > OHof H+ and • H+ < OHOH- ions
• H+ = OH-
Arrhenius vs Bronstead-Lowry
an acid is a
States that an acid
substance that
is a hydrogen-ion
ionizes to produce donor
hydrogen ions in
aqueous solution
a base dissociates to a base is a hydrogenproduce a hydroxide ion acceptor
ion in aqueous
solution
Amphoteric Substances
 Amphoteric-
a substance that can
act as both acids and bases
–Ex: Water
When HF dissolves in water,
water acts as base
When NH3 dissolves in water,
water acts as acid
Strong Acids vs Weak Acids
–http://www.mhhe.com/physsci/che
mistry/chang7/esp/folder_structure
/ac/m2/s1/index.htm
19.2 Strengths of Acids
Strong Acids
acid that ionizes
completely
Weak Acids
acid that ionizes only
partially in dilute aqueous
solutions
Ex: HC2H3O2, H2CO3
Good conductors of
Poor conductors of
electricity, makes great
electricity
electrolytes
Ex: HCl, HNO3, H2SO4
Reactions shown
Reactions shown with
with 
>
Strong Base vs Weak Base
–http://www.mhhe.com/physsci/che
mistry/chang7/esp/folder_structure
/ac/m2/s2/index.htm
19.2 Strengths of Bases
Strong Base
dissociate completely
into metal ions and
hydroxide ions
Ex: NaOH, Ca(OH)2
Weak Base
ionizes only partially in
dilute aqueous solutions
to form conjugate acid
of the base and
hydroxide ion
Ex: CH3NH2
19.3 What is pH?
 Pure
water contains equal
numbers of H+ and OH- ions
 Kw = [H+] [OH-]
 Use 1.0x10-14 M for Kw
Ion Product Constant of Water
 Ion
Product Constant of WaterKw- the value of the equilibrium
constant for water
 At 298 K, Kw is 1.0 x 10-14
 Kw = [H+] [OH-]
pH
 pH-
the negative logarithm of the
hydrogen ion concentration
 pH = -log [H+]
Math Calculations
pH + pOH = 14
 pH= -log(H+)
 pH when given pOH = 14- (-log OH)

pH Scale
 pH
below 7 is an acid
 pH above 7 is a base
 pH = 7 is neutral
pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
pH Scale

http://www.purchon.com/chemistry/flash/
ph.swf
19.4 Neutralization
 Neutralization
Reaction- acid &
base react to produce a salt &
water
–a Double-Replacement Reaction
 Salt-
an ionic compound formed
from the cation of a base & anion
of an acid
 Acid-Base
Indicator- a compound
that changes color as it is placed
in either an acid or base
Titration

The process in which an acid-base
neutralization reaction is used to
determine the concentration of a solution
of unknown concentration.
End Point

The point at which an indicator used in a
titration changes color
Buffers

A solution that resists changes in pH when
limited amounts of acids and bases are
added.