Acids And Bases

1
Acids And Bases
2
Class question

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

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

3
Properties of Acids

• Taste sour
• React with bases
• Litmus paper test turn blue litmus paper red
• Electrolytic conduct electricity

4
Properties of Bases

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

5
Nomenclature of Acids

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

Hydrogen ion (H)
anion
H Cl1-
HCl
Ex
H SO42-
H2SO4
6
Binary AcidsH anion

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

Hydro _____ic acid
chloride
Hydrochloric acid
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Binary Acids H anion

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

Hydro _____ic acid
fluoride
Hydrofluoric acid
8
OxyacidsH anion

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

_____ic acid
nitrate
nitric acid
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Oxyacids H anion

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

_____ic acid
sulfate
sulfuric acid
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Oxyacids H anion

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

_____ous acid
nitrite
nitrous acid
11
Oxyacids H anion

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

_____ous acid
chlorite
chlorous acid
12
Writing acid formulas

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

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

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

cation
hydroxide (OH1-)
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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
15
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
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Ions In Solution

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

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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

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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

19
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

20
Self Ionization of Water

• Proper ionization
• H2O H2O ?

H3O OH-
hydronium ion
H
O

?
O

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

• simplified version
• H2O ?

H OH-
22
Types of Acids/Bases

• Arrhenius Model
• Bronsted-Lowry Model
• Lewis Model

23
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-
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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-
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Flaw with Arrhenius model

• Not all bases contain hydroxide
• Ex ammonia (NH3) is basic
• Therefore a new type of acid/base must be
  determined

26
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

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Bronsted-Lowry Model

• REMEMBER!!!! REMEMBER!!!!
• acids donate, bases accept protons
• Abigail doesnt buy apples.

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Bronsted-Lowry Model

• Examples
• HCl H2O ? Cl- H3O

What is happening here?
Acid (donates proton)
Base (accepts proton)
Which is the acid? base?
29
Bronsted-Lowry Model

• Examples
• NH3 H2O ? NH4 OH-

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

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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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Conjugate Acid/Base Pairs

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

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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.
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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
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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
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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?
37
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?
38
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 is acts as a base in
one reaction and acts as an acid in the second
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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)

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Polyprotic Acid Ionization

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

H2PO41- H
HPO42- H
PO43- H
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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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Strong Acid

• Illustration

-

H
H
A
A

-

H
H
A
A

-

H
H
A
A
All break into ions
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Strength of Acids and Bases

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

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6 Strong Acids

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

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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
46
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

47
Weak Acid

• Illustration

-

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

• The ones that are NOT strong

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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
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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
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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
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Ion Product Constant for Water (Kw)

• in pure water ?
• H OH- 1 x 10-7 M
• 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
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Is solution acidic, basic, or neutral?

• Acidic
• Basic
• neutral

H gt OH-
H lt OH-
H OH-
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pH and pOH

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

ACIDIC
BASIC
0
7
14
pH
(neutral)
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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

57
pOH

• Formula -log OH-

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Relation of pH and pOH

• pH pOH 14

If given one variable, subtract to find the other
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Overall Relationship
pH
pOH
H
OH-
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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

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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

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Sample problem 2

• pH pOH 14
• pH 5.09 14
• pH 8.91

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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

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Sample problem 3

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

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Sample problem 4

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

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Sample problem 4

• (ii) What is the pH?

• pH pOH 14.0
• pH 3.7 14.0
• pH 10.3

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Sample problem 4

• (iii) What is the H ?
• H 10-pH
• 10-10.3
• 5.01 x 10-11 M

68
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

69
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
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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
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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
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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
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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 ____________
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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 ____________
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Acid-Base Indicator

• A compound that will change color as the pH
  changes
• Phenolphthalein changes between clear and pink
• Hydrangeas grow pink or blue depending on the pH
  of their soil

76
How does an indicator work?

• Indicators are weak acids or weak bases. In the
  acid form they have one color. When they switch
  to the base form they have a different color.

77
Titration

• The controlled addition and measurement of the
  amount of a solution of known concentration
  required to react completely with a measured
  amount of a solution of unknown concentration.

78
Why do we use titrations?

• To experimentally determine the concentration of
  a solution
• The bottle wasnt labeled
• The label faded
• Your chemistry teacher is evil

79
How do we conduct a titration?

1. Measure a volume of the solution of unknown
   concentration into a flask.
2. Add 3 to 5 drops of indicator.
3. While stirring slowly add a measured volume of
   the solution of known concentration to the flask.
4. Use math to find the concentration you dont know.

Read pages 500 501 for a more detailed
explanation, including pictures showing this
process.
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Equivalence point

• Moles of hydrogen ions moles of hydroxide ions
• Use normality, not molarity
• NaVa NbVb

Accounts for polyprotic acids multiply the
molarity by the number of hydrogens available
81
End Point

• When the indicator changes color
• This is when you stop adding the known into the
  unknown
• Use the volume at the end point for your
  calculations

82
Sample Problem

• In a titration, 25.0 mL of 0.0350 M Ba(OH)2
  neutralizes 16.5 mL of HCl solution. What is the
  molarity of the HCl solution?

83
Sample Problem

• In a titration, 25.0 mL of 0.0350 M Ba(OH)2
  neutralizes 16.5 mL of HCl solution. What is the
  molarity of the HCl solution?
• Nb 0.0350 2 0.0700
• (2 hydroxides in each one)

84
Sample Problem

• In a titration, 25.0 mL of 0.0350 M Ba(OH)2
  neutralizes 16.5 mL of HCl solution. What is the
  molarity of the HCl solution?
• Nb 0.0350 2 0.0700

85
Sample Problem

• In a titration, 25.0 mL of 0.0350 M Ba(OH)2
  neutralizes 16.5 mL of HCl solution. What is the
  molarity of the HCl solution?
• Nb 0.0350 2 0.0700