Catalyst
 Rate yourself on LTs 7.9, 7.10, 7.11, and 7.13
End
Dry Ice and Universal Indicator
Today’s Learning Targets
 LT 7.9 – I can compare and contrast the Arrhenius, Bronsted –
Lowry, Lewis definition of acids and bases
 LT 7.10 – I can compare and contrast the similarities and
differences between a strong acid/base and a week acid/base.
 LT 7.11 – I can calculate the pH or pOH of a strong acid/base.
 LT 7.13 – I can identify the conjugate acid/base pair in a chemical
reaction. Furthermore, I can use this definition to explain the
amphoteric nature of water.
Layout of Today’s Class
 Independent Review of Acids/Bases from last year using the
website
 Packet must be completed by the end of class.
 You may do the review online or you can participate in one or
more of the small “mini – lectures”
 Lecture 1 (LT 7.9) – Arrhenius, Bronsted Lowry, and Lewis acids and
bases
 Lecture 2 (LT 7.10) – Strong vs. Weak acids/bases
 Lecture 3 (LT 7.11) – pH, pOH, and calculating pH/pOH
 Lecture 4 (LT 7.13) – Conjugate Acids/Bases (Only covered in
honors last year)
Neutralization Reactions
 Recall, one of the most common types of reactions are acid/base
reactions or neutralization reactions
 We have various definitions of acids and bases, but they all react
with characteristic properties.
 NOTE –We will review some of the material from last year, but it
is expected that you study all material previously taught.
Arrhenius Acid/Base
 Arrhenius’ theory of acids/bases
focuses on what molecules contain
 An Arrhenius acid contains a H+
 An Arrhenius base contains an
OH-
Bronsted – Lowry Acid/Base
 When Arrhenius’ definition covers
many acids/bases, acid/base reactions
are not about containing H+ or OH A Bronsted-Lowry acid is any
compound that gives H+ during the
reaction
 A Bronsted-Lowry base is any
compound that accepts H+ during the
reaction.
 We will use this definition most of the
time in this class
Lewis Acid/Base
 Ultimately, acid/base reactions are




not about H+, but about the
accepting or donating of electron
pairs.
A Lewis acid is an electron pair
acceptor
A Lewis base is an electron pair
donor
Every acid/base in the previous two
categories are also acids/bases in
this category
Broadest definition
Class Example
 Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or
Lewis:
Table Talk
 Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or
Lewis:
Strong vs. Weak Acid/Base
• Acids/Bases can be classified as strong or weak based on how
much it disassociates.
• Disassociate – To break apart
• Acids/Bases that completely dissociate are called strong
acids/bases
• Acids/Bases that only partially dissociate are called weak
acids/bases. These are in equilibrium with one
another
Dissociation
Strong Acids/Strong Bases to Memorize
Strong Bases
Strong Acids
1.
2.
3.
4.
5.
6.
7.
8.
LiOH
NaOH
KOH
RbOH
CsOH
Ca(OH)2
Sr(OH)2
Ba(OH)2
1.
2.
3.
4.
5.
6.
7.
HBr
HCl
HI
HNO3
H2SO4
HClO3
HClO4
I. pH
 The concentrations of acids and
bases are often very low.
 We use the pH scale to convey the
concentration of H+
 The pH scale is 0-14.
 Acid = pH 0-7
 Base
= pH 7-14
 Neutral chemicals = pH of 7.
pH/pOH
 We calculate the pH by:
pH=-log([H+])
 We calculate pOH by:
pOH=-log([OH-])
 For strong acids and bases, the
concentration of the compound is the [H+]
or [OH-]
 For bases, we only know [OH-], so we need
to first calculate pOH and then convert to
pH using the equation:
pH = 14 – pOH
Class Example
 What is the pH of a 0.231 M solution of NaOH?
Table Talk
 What is the pH of a 0.512 M solution of HNO3?
Conjugate Acid/Base Pairs
 As with any reaction, there is a forward and reverse reaction for




acid/base reactions.
Consider the following example:
HX + H2O ⇌H3O+ + XIn the forward reaction HX is the acid because it donates H+ and
H2O is the base because it accepts H+.
In the reverse reaction, H3O+ is now the acid and X- is now the
base.
The pair of HX and X- are known as an conjugate acid-base
pair
Conjugate Acid/Base Pairs
 Every acid has a conjugate base that is formed when a proton
(H+) is removed
 Every base has a conjugate acid that forms when a proton is
added
Class Example
 Identify the acid, base, conjugate acid, and conjugate base in the
following reaction. Identify the acid/base as Arrhenius, Bronsted –
Lowry, and/or Lewis:
NH3 + H2O  NH4+ + OH-
Table Talk
 Identify the acid, base, conjugate acid, and conjugate base in the
following reaction. Identify the acid/base as Arrhenius, Bronsted –
Lowry, and/or Lewis:
HSO3- + H2O  SO32- + H3O+
Exit Ticket
1 Identify the acid, base, conjugate acid, and conjugate base in the
reaction below. Furthermore, identify the acid and base as
either Arrhenius, Bronsted – Lowry, Lewis, or some
combination of the 3.
HCl + NH3  NH4+ + Cl2. What is the difference between a strong acid and a weak acid?
3.You have a 0.42 M solution of NaOH. What is the pH? Is it
acidic, basic, or neutral?
Closing Time
 Read: 15.6, 15.7, 16.1, 16.2, and 16.11
 Homework: