Acids And Bases

1
Acids And Bases
2
Section 19.1Acid-Base Theories

• OBJECTIVES
• Define the properties of acids and bases.

3
Section 19.1Acid-Base Theories

• OBJECTIVES
• Compare and contrast acids and bases as defined
  by the theories of a) Arrhenius,
  b) Brønsted-Lowry, and c)
  Lewis.

4
Class question

• Where can acids be found?
• Sodas
• Stomach
• Vinegar
• Citrus fruits

• Where can bases be found?
• Soap
• Drano
• Antacid tablets
• Windex
• detergent

5
Properties of Acids

• Taste sour
• React with bases
• Litmus paper test turn blue litmus paper red
• Electrolytic conduct electricity
• Can be strong or weak electrolytes in aqueous
  solution

6
Properties of Acids

• They have a pH of less than 7 (more on this
  concept of pH in a later lesson)
• How do you know if a chemical is an acid?
• It usually starts with Hydrogen.
• HCl, H2SO4, HNO3, etc. (but not water!)

7
Acids Affect Indicators, by changing their color
Blue litmus paper turns red in contact with an
acid (and red paper stays red).
8
Acids have a pH less than 7
9
Properties of Bases

• Taste bitter
• Feels slippery
• React with acids
• Litmus paper test turn red litmus paper blue
• electrolytic

10
Bases Affect Indicators
Red litmus paper turns blue in contact with a
base (and blue paper stays blue).
Phenolphthalein turns purple in a base.
11
Bases have a pH greater than 7
12
Acid Nomenclature
13
Nomenclature of Acids

• Acids are composed of a(n)
• ________________ followed by
• a(n) _______

Hydrogen ion (H)
anion
H Cl1-
HCl
Ex
H SO42-
H2SO4
14
Binary AcidsH anion

• H anion with ide ending ?
• acid name is __________________
• HCl anion? _______
• acid name ________________

Hydro _____ic acid
chloride
Hydrochloric acid
15
Binary Acids H anion

• H anion with ide ending ?
• acid name is __________________
• HF anion? _______
• acid name ________________

Hydro _____ic acid
fluoride
Hydrofluoric acid
16
OxyacidsH anion

• H anion with ate ending ?
• acid name is __________________
• HNO3 anion? _______
• acid name ________________

_____ic acid
nitrate
nitric acid
17
Oxyacids H anion

• H anion with ate ending ?
• acid name is __________________
• H2SO4 anion? _______
• acid name ________________

_____ic acid
sulfate
sulfuric acid
18
Oxyacids H anion

• H anion with ite ending ?
• acid name is __________________
• HNO2 anion? _______
• acid name ________________

_____ous acid
nitrite
nitrous acid
19
Oxyacids H anion

• H anion with ite ending ?
• acid name is __________________
• HClO2 anion? _______
• acid name ________________

_____ous acid
chlorite
chlorous acid
20
Writing acid formulas

• Hydrobromic acid
• anion? ___________ formula ______
• Acetic acid
• anion? ___________ formula ______
• Nitrous acid
• anion? ___________ formula ______

HBr
Bromide (Br1-)
HC2H3O2
acetate(C2H3O21-)
HNO2
nitrite (NO21-)
21
Base Nomenclature
22
Nomenclature of Bases

• Bases are composed of a(n)
• _______ followed by
• a(n) ________________

cation
hydroxide (OH1-)
23
Writing Base Names

• Rule name the cation and add hydroxide
• NaOH
• Mg(OH)2
• Fe(OH)3

sodium hydroxide
magnesium hydroxide
Iron (III) hydroxide
Memorize NH3 ammonia
24
Writing base formulas

• potassium hydroxide
• cation? ______ formula ______
• Calcium hydroxide
• cation? ______ formula ______
• Aluminum hydroxide
• cation? ______ formula ______

KOH
K
Ca(OH)2
Ca2
Al(OH)3
Al3
25
Ions In Solution

• Why are some solutions acidic, basic, or neutral?
• It depends on number of H and OH- ions present.

26
Ions In Solution

• Acidic solution contain more H ions than OH-
  ions
• 4000 H and 0 OH- is acidic
• 1000 H and 500 OH- is acidic
• 5 H and 3 OH- is acidic

27
Ions In Solution

• Basic Solution contain more OH- ions than H
  ions
• 4000 OH- and 0 H is basic
• 1000 OH- and 500 H is basic
• 5 OH- and 3 H is basic

28
Ions In Solution

• Neutral Solution equal amounts of H and OH-
  ions
• 4000 OH- and 4000 H is neutral
• 1000 OH- and 1000 H is neutral
• 5 OH- and 5 H is neutral

29
Self Ionization of Water

• Proper ionization
• H2O H2O ?

H3O OH-
hydronium ion
H
O

?
O

H
O
H
H
H
H
O
H
H
30
Self Ionization of Water

• simplified version
• H2O ?

H OH-
31
Acid-Base Theories
32
Types of Acids/Bases

• Arrhenius Model
• Bronsted-Lowry Model
• Lewis Model

33
Svante Arrhenius

• He was a Swedish chemist (1859-1927), and a Nobel
  prize winner in chemistry (1903)
• one of the first chemists to explain the chemical
  theory of the behavior of acids and bases
• Dr. Hubert Alyea (professor emeritus at Princeton
  University) was the last graduate student of
  Arrhenius.

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Hubert N. Alyea (1903-1996)
35
Svante Arrhenius (1859-1927)
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Arrhenius Model of Acids and Bases

• Arrhenius Acids
• Defn contain H and ionizes to form H
• Examples
• HCl ?
• HNO3 ?

makes solution ACIDIC
H Cl-
H NO3-
37
Arrhenius Model of Acids and Bases

• Arrhenius Bases
• Defn
• contain OH- and ionizes to produce OH- ions
• Examples
• NaOH ?
• Ca(OH)2 ?

makes solution BASIC
Na OH-
Ca2 2 OH-
38
Flaw with Arrhenius model

• Not all bases contain hydroxide
• Ex ammonia (NH3) is basic
• According to Arrhenius, since ammonia can NOT
  produce OH- it is NOT a base
• Therefore a new type of acid/base must be
  determined

39
Gilbert Lewis (1875-1946)
40
Lewis Acids and Bases

• Gilbert Lewis focused on the donation or
  acceptance of a pair of electrons during a
  reaction
• Most general of all 3 definitions acids dont
  even need hydrogen!

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Lewis Model

• Lewis acid
• an atom, ion, or molecule that accepts an
  electron pair to form a covalent bond
• Lewis base
• An atom, ion, or molecule that donates an
  electron pair to form a covalent bond

42
Lewis Model

• Lewis acid-base reaction
• The formation of one or more covalent bonds
  between an electron-pair donor and an
  electron-pair acceptor

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Example

• Acids are electron pair acceptors.
• Bases are electron pair donors.

Lewis base
Lewis acid
44
Johannes Brønsted Thomas Lowry
(1879-1947) (1874-1936)
Denmark England
45
Bronsted-Lowry Model

• Bronsted-Lowry Acid
• Defn proton/H donor
• can give H to another species
• Bronsted-Lowry Base
• Defn proton/H acceptor
• can take H from another species

Acids and bases always come in pairs.
46
Bronsted-Lowry Model

• REMEMBER!!!! REMEMBER!!!!
• acids donate, bases accept protons
• Ashley does boys always

47
Bronsted-Lowry Model

• Examples
• HCl H2O ? Cl- H3O

What is happening here?
Acid (donates proton)
Base (accepts proton)
Which is the acid? base?
Water is a basewhen the HCl gives up the proton,
water accepts it to form the hydronium ion
HCl is an acid when it dissolves in water, it
gives its proton to water.
48
Bronsted-Lowry Model

• Examples
• NH3 H2O ? NH4 OH-

What is happening here?
Acid (donates proton)
Base (accepts proton)
Which is the acid? base?
49
Why Ammonia is a Base

• Ammonia can be explained as a base by using
  Brønsted-Lowry
• NH3(aq) H2O(l) ? NH41(aq) OH1-(aq)
• Ammonia is the hydrogen ion acceptor (base), and
  water is the hydrogen ion donor (acid).

50
Conjugate Acid/Base Pairs

• Conjugate acid new species produced when base
  gains H ion
• Conjugate base new species produced when acid
  donates H ion

Thus, a conjugate acid-base pair is related by
the loss or gain of a single hydrogen ion.
51
Conjugate Acid/Base Pairs

• general Bronsted-Lowry reaction
• acid base ? conj. acid conj. base

conj. acid/base pair
conj. acid/base pair
Every acid has a conjugate base. Every base has a
conjugate acid.
52
Conjugate Acid/Base Pairs

• Examples
• HNO3 H2O ? H3O NO3-

What is the acid? base?
conj. acid/base pair
C.A.
C.B.
acid
base
What is the conjugate acid/base?
conj. acid/base pair
53
Conjugate Acid/Base Pairs

• Examples
• NH3 H2O ? NH4 OH-

What is the acid? base?
conj. acid/base pair
acid
base
C.B.
C.A.
What is the conjugate acid/base?
conj. acid/base pair
54
Conjugate acid-base pairs

• What is the conjugate base of
• H2SO4 _________ H3O ________
• What is the conjugate acid of
• HPO42- _________ OH1- ________

HSO41-
H2O
H2PO41-
H2O
How can H2O be both acid and base?
55
What is the conjugate base?

• Acid Conjugate Base
• H2SO4
• HPO42-
• NH41
• H3O1
• H2O

HSO41-
PO43-
NH3
H2O
OH-
How can H2O be both acid and base?
56
Acids and bases come in pairs

• General equation is
• HA(aq) H2O(l) ? H3O(aq) A-(aq)
• Acid Base ? Conjugate acid Conjugate base
• NH3 H2O ? NH41 OH1-
• base acid c.a. c.b.
• HCl H2O ? H3O1 Cl1-
• acid base c.a. c.b.

57
Amphoteric

• Defn substance that can act as both acids and
  bases
• HNO3 H2O ? H3O NO3-
• NH3 H2O ? NH4 OH-

Is H2O a base or acid?
base
Is H2O a base or acid?
acid
Water is amphoteric b/c it acts as a base in one
reaction and acts as an acid in the second
58
Mono-, Di-, Triprotic Acids

• Defns
• monoprotic (HA) one ionizable proton
• ex HF, HCl, HBr ( normality is 1)
• diprotic (H2A) two ionizable protons
• ex H2SO4, H2CO3 ( normality is 2)
• triprotic (H3A) three ionizable protons ex
  H3PO4, H3BO3 ( normality is 3)

59
Polyprotic Acid Ionization

• Always forms ONE H
• H3PO4 ?
• H2PO41- ?
• HPO42- ?

H2PO41- H
HPO42- H
PO43- H
60
Strength of Acids and Bases

• Acid/base strength is based on ? the degree to
  which they ionize
• 1) strong (?)
• 2) weak (?)

61
Strong Acid/Base

• Defn acid or base that completely ionizes
• HA H A-
• XOH X OH-

100
ionization
100
ionization
?every single HA molecule ionizes into H and A-
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Strength

• Strong Acid/Base
• 100 ionized in water
• strong electrolyte

HCl HNO3 H2SO4 HBr HI HClO4
NaOH KOH Ca(OH)2 Ba(OH)2
63
Strong Acid

• Illustration

-

H
H
A
A

-

H
H
A
A

-

H
H
A
A
All break into ions
64
6 Strong Acids

• HCl hydrochloric acid
• HBr hydrobromic acid
• HI hydroiodic acid
• HClO4 perchloric acid
• H2SO4 sulfuric acid
• HNO3 nitric acid

65
Strong Bases

• Group I and II metal hydroxides

LiOH NaOH KOH RbOH
Mg(OH)2 Ca(OH)2 Sr(OH)2 Ba(OH)2
No need to memorize exact ones
66
Weak Acid/Base

• Defn acid or base that partially ionizes
• HA H A-
• XOH X OH-

partial
ionization

• not all will ionize the weaker it is
• the less it ionizes

67
Strength

• Weak Acid/Base
• does not ionize completely
• weak electrolyte
• Dissociates into both ions and molecules

HF CH3COOH H3PO4 H2CO3 HCN
NH3
68
Weak Acid

• Illustration

-

H
H
A
A
H
H
A
A
H
H
A
A
Only some break into ions
69
What are the weak acids and bases?

• The ones that are NOT strong

70
Strong or weak, concentrated or diluted

• For acids and bases, it is important to
  distinguish between concentrated and dilute from
  strong and weak. The words _________ and
  __________
• have different meanings. Similarly, ___________
  and ___________ are not the same either.

strong
concentrated
weak
dilute
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Strong or weak, concentrated or diluted

• Strong and weak refer to
• ____________________________
• Concentrated and dilute refer to
• ____________________________

how much substance ionizes
how much solute is present
72
Example

• 1 M HCl
• 12 M HCl
• 1 M H2CO3
• 12 M H2CO3

Strong and dilute
Strong and concentrated
weak and dilute
weak and concentrated
73
Ion Product Constant for Water (Kw)

• Defn equilibrium value for self ionization of
  water (H2O ? H OH-)
• Formula
• Kw HOH- 1 x 10-14

ALWAYS ALWAYS ALWAYS
74
Ion Product Constant for Water (Kw)

• in pure water ?
• H OH- 1 x 10-7
• in non pure water ?
• (acidic/basic conditions), value of H and
  OH- differ

Remember pure water is neutral
But still HOH- 1 x 10-14
75
Is solution acidic, basic, or neutral?

• Acidic
• Basic
• neutral

H gt OH-
H lt OH-
H OH-
76
The pH Scale

0
14
7
INCREASING ACIDITY
INCREASING BASICITY
NEUTRAL
pH -log H
77
The pH Scale

• pH of Common Substances

78
Relation of pH and pOH

• pH pOH 14

If given one variable, subtract to find the other
79
The pH Scale
pH -logH pOH -logOH- pH pOH 14
80
pH and pOH

• pH
• Defn pH -log H
• Scale range from 0 to 14

ACIDIC
BASIC
0
7
14
pH
(neutral)
81
pH

• c) change one pH unit ?
• represents a ten fold change in strength
• - ex pH 3 vs pH 4
• pH 3 is 101 or 10 times more acidic
• - ex pH 7 vs pH 10
• pH 7 is 103 or 1000 times more acidic

82
pOH

• Formula -log OH-

83
Overall Relationship
pH
pOH
H
OH-
84
Overall Relationship
85
The pH Scale

• What is the pH of 0.050 M HNO3?

pH -logH pH -log0.050 pH 1.3 Acidic
or basic?
Acidic
86
Calculating H and OH-

• Find the hydroxide ion concentration of 3.0 ?
  10-2 M HCl.

HOH- 1.0 ? 10-14 3.0 ? 10-2OH- 1.0 ?
10-14 OH- 3.3 ? 10-13 M Acidic or basic?
Acidic
87
Calculating H and OH-

• What is the molarity of HBr in a solution that
  has a pOH of 9.6?

pH pOH 14 pH 9.6 14 pH 4.4
pH -logH 4.4 -logH -4.4 logH H
4.0 ? 10-5 M HBr
Acidic
88
Calculating H and OH-

• A Ca(OH)2 solution has a pH of 8.0. Determine the
  H, OH-, and Ca(OH)2 for the solution.
• pH - log H
• log H -pH
• H antilog (-pH) antilog (-8.0)
  1 x 10-8 M H3O

Antilog is the same thing as 10(x)
89
Calculating H and OH-

• H OH- 1 x 10-14 M2
• OH- 1 x 10-14 M2 1 x 10-14 M2
• H 1 x 10-8 M
• OH- 1 x 10-6 M

90
Calculating H and OH-

• Ca(OH)2 Ca2 2OH-
• ( 1 x 10-6
  M)
• 1 x 10-6 mol OH- 1 mol Ca(OH)2 5 x 10-7 mol/L
  Ca(OH)2
• Liter 2 mol OH-
• Ca(OH)2 5 x 10-7 M

91
Sample problem 1

• Calculate the pH of a solution with H 3.0 x
  10-6 M.
• pH -log H
• - log 3.0 x 10-6
• 5.52

92
Sample problem 2

• Calculate the pH of a solution with OH- 8.2 x
  10-6.
• pOH -logOH-
• -log 8.2 x 10-6
• 5.09

OH- ? pOH ? pH
pH pOH 14 pH 5.09 14 pH 8.91
93
Sample problem 2

• Calculate the pH of a solution with OH- 8.2 x
  10-6.
• HOH- 1 x 10-14
• H8.2 x 10-6 1 x 10-14
• H 1.22 x 10-9
• pH -log1.22 x 10-9 8.91

OH- ? H ? pH
94
Sample problem 3

• What is the H of a solution with pH 2?
• pH -logH
• H 10-pH
• 10-2
• 0.01 M

95
Sample problem 4

• (i) What is the OH- of a solution with pOH
  3.7?
• OH- 10-pOH
• OH- 10-3.7
• 2 x 10-4 M

96
Sample problem 4

• (ii) What is the pH and the H if the pOH is
  3.7?

pOH ? pH ? H

• H 10-pH
• 10-10.3
• 5 x 10-11 M

• pH pOH 14
• pH 3.7 14
• pH 10.3

97
Reaction between acids and bases

• Neutralization (defn) reaction of acid and base
  to form a salt and water
• The reaction is a double replacement
• Salt (defn) ionic compound made of
• cation from base and
• anion from acid

98
Reaction between acids and bases

• Ex reaction
• Mg(OH)2 HCl ?

MgCl2 H2O
base
acid
salt
water
Mg2 OH-
H Cl-
Mg2 - cation from base Cl- - anion from acid
99
Neutralization

• ACID BASE ? SALT WATER

HCl NaOH ? NaCl H2O
strong
strong
neutral
HC2H3O2 NaOH ? NaC2H3O2 H2O
weak
strong
basic

• Salts can be neutral, acidic, or basic.

• Neutralization does not mean pH 7.

100
Ex problems

• i) What is the salt formed from sulfuric acid
  (H2SO4) and potassium hydroxide (KOH)?
• base cation?
• acid anion?

K
SO42-
What is salt?
K2SO4
101
Ex problems

• ii) What is the salt formed when Al(OH)3 and HBr
  react?
• base cation?
• acid anion?

Al3
Br-
What is salt?
AlBr3
102
Is salt solution acidic, basic, or neutral?

• a) strong acid strong base ?
• b) strong acid weak base ?
• c) weak acid strong base ?

Neutral salt
acidic salt
basic salt
103
Ex problem

• Determine if salt solution is acidic, basic, or
  neutral.
• LiBr
• acid?
• base?

? Li Br-
HBr
(strong acid)
(strong base)
LiOH
NEUTRAL
Salt is ____________
104
Ex problem

• Determine if salt solution is acidic, basic, or
  neutral.
• b) Fe(NO3)3
• acid?
• base?

? Fe3 NO3-
HNO3
(strong acid)
(weak base)
Fe(OH)3
ACIDIC
Salt is ____________
105
B. Titration

• Titration
• Analytical method in which a standard solution is
  used to determine the concentration of an unknown
  solution.

106
B. Titration

• Equivalence point (endpoint)
• Point at which equal amounts of H3O and OH- have
  been added.
• Determined by
• indicator color change

• dramatic change in pH

107
Titration

• dramatic change in pH

108
B. Titration
moles H3O moles OH- M?V? n M?V? n
M Molarity V volume n of H ions in the
acid or OH- ions in the base
109
Titration

• 42.5 mL of 1.3M KOH are required to neutralize
  50.0 mL of H2SO4. Find the molarity of H2SO4.

H3O M ? V 50.0 mL n 2
OH- M 1.3M V 42.5 mL n 1
MV MV M(50.0mL)(2) (1.3M)(42.5mL)(1) M
0.55M H2SO4
Subscript of H or OH from formulas!