Chapter 4: Reactions in Aqueous Solutions

1
Chapter 4 Reactions in Aqueous Solutions

• Electrolytes vs. Nonelectrolytes
• Precipitation Reactions
• Solubility Rules
• Acid-Base Reactions
• Neutralization
• Acid and Carbonate
• Acid and Metal
• Oxidation-Reduction Reactions

2
Chapter 4 Reactions in Aqueous Solutions

• IV. Concentration of Solutions
• Solution Stoichiometry

3
A solution is a homogenous mixture of 2 or more
substances
The solute is(are) the substance(s) present in
the smaller amount(s)
The solvent is the substance present in the
larger amount
In aqueous solutions (aq) solvent is
water solute can be ionic compounds, aqueous
acids, bases, or molecular compounds
4.1
4
Types of Solutions

• air O2 gas and N2 gas gas/gas
• soda CO2 gas in water gas/liquid
• seawater NaCl in water solid/liquid
• brass copper and zinc solid/solid

5
Nature of Solutes in Solutions

• Spread evenly throughout the solution
• Cannot be separated by filtration
• Can be separated by evaporation
• Not visible, solution appears transparent
• May give a color to the solution

6
Water

• Most common solvent
• A polar molecule
• O? -
• a hydrogen bond
• H?
• H?

7
Hydrogen Bonds Attract Polar Water Molecules

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Surface Tension

• Water molecules within water hydrogen bond in all
  directions
• Water molecules at surface cannot hydrogen bond
  above the surface, pulled inward
• Water surface behaves like a thin, elastic
  membrane or skin
• Surfactants (detergents) undo hydrogen bonding

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meniscus
12
Like dissolves like

• A solvent such as water is needed to dissolve
  polar solutes such as sugar and ionic solutes
  such as NaCl.
• A solvent such as hexane (C6H14) is needed to
  dissolve nonpolar solutes such as oil or grease.

13
Learning Check SF4

• Which of the following solutes will dissolve in
  water? Why?
• 1) Na2SO4
• 2) gasoline
• 3) I2
• 4) HCl

14
Solution SF4

• Which of the following solutes will dissolve in
  water? Why?
• 1) Na2SO4 Yes, polar (ionic)
• 2) gasoline No, nonnpolar
• 3) I2 No, nonpolar
• 4) HCl Yes, Polar

15
An electrolyte is a substance that, when
dissolved in water, results in a solution that
can conduct electricity.
A nonelectrolyte is a substance that, when
dissolved, results in a solution that does not
conduct electricity.
16
Electrolytes

• Are substances that form positive() and negative
  (-) ions in water
• Conduct an electric current

17
Electrolytes in the Body

• Carry messages sent to and from the brain as
  electrical signals.
• Maintain cellular function with the correct
  concentrations electrolytes.

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Nonelectrolytes

• Dissolve as molecules only
• No ions are produced in water
• Do not conduct an electric current
• C6H12O6 (s) ?? C6H12O6 (aq)
• glucose

H2O
19
4 Types of Inorganic Compounds

• Molecular Made of 2 or more nonmetals
• Ionic Made of cations and anions. Generally,
  the cation is from a metal and anion is from a
  nonmetal or polyatomic ion.
• Base A substance which is a proton (H)
  acceptor.
• Acid A substance which is a proton donor.

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Sodium Chloride Structure
mp 808 ºC
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Formation of a Solution

H2O
Hydration
Na
Cl-
Na
Dissolved solute
Cl-
H2O
Na
Cl-
solute
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A Water Solution of Sodium Chloride

• hydrated ions
• Lowers freezing point
• Raises boiling point
• Conductive as a solution
• Ions not created, simply unfrozen

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A Water Solution of Sodium Chloride
24
Writing An Equation for a Solution

• When NaCl(s) dissolves in water, the reaction
  can be written as
• H2O
• NaCl(s) Na (aq) Cl- (aq)
• solid separation of ions in
  water

Dissociation
25
Learning Check SF5

• Solid LiCl is added to some water. It dissolves
  because
• A. The Li ions are attracted to the
• 1) oxygen atom(??-) of water
• 2) hydrogen atom(?) of water
• B. The Cl- ions are attracted to the
• 1) oxygen atom(??-) of water
• 2) hydrogen atom(?) of water

26
Solution SF5

• Solid LiCl is added to some water. It dissolves
  because
• A. The Li ions are attracted to the
• 1) oxygen atom(??-) of water
• B. The Cl- ions are attracted to the
• 2) hydrogen atom(?) of water

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Water solutions of Other Salts
28
Solubility Equilibria for Ionic Compounds
If 6.10 moles of NaCl is dissolved in 1,000 g H2O
at 0ºC, no salt crystallizes.
If gt 6.10 moles at 0ºC, 6.10 moles of NaCl
remains, the rest crystallizes.
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Inorganic Compounds Dissolved in WaterALL BUT
MOLECULAR PRODUCE IONS

• Ionic Compounds
• Na Cl (aq)

2. Bases Na (OH) (aq)
Cl-
OH-
Na
Na
3. Aqueous Acids HCl (aq)
4. Molecular ICl (aq)
NO Ions!
Cl-
Cl
H
I
30
4.1
31
Electrolytic Solutions Contain Mobile Cations ()
and Anions(-)

• Ionic compounds, aqueous acids, and bases
  dissociate into the ions they are made of when
  dissolved in water.
• NaCl (s) ? Na (aq) Cl-(aq)
• More ions in solution, stronger electrolyte

H2O
32
Weak vs. Strong Electrolyte A strong electrolyte
will produce more ions when same amount of solid
is dissolved in solvent.
Strong Electrolyte 100 dissociation
HCl (g) H (aq) Cl- (aq)
H2O
Weak Electrolyte not completely dissociated
HNO2
H
NO2-
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Strong Electrolytes are 100 ionized

• salts 100ions
• NaCl(s) Na(aq) Cl-(aq)
• CaBr2(s) Ca2(aq) 2Br- (aq)
• acids
• HCl(g) H3O(aq) Cl-(aq)

H2O
H2O
H2O
34
Weak electrolytes

• Most of the solute exists as molecules in
  solution
• Only a few solute particles produce ions
• HF H2O H3O(aq) F-
  (aq)
• acid
• NH3 H2O NH4(aq) OH-
  (aq)
• base

35
Precipitation Reactions

• Mix two aqueous solutions made by dissolving
  ionic compounds in water.
• If a reaction happens, a precipitate (solid) is
  formed.

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Soluble and Insoluble Salts

• A soluble salt is an ionic compound that
  dissolves in water.
• An insoluble salt is an ionic compound that does
  not dissolve in water

39
Predicting Products of Precipitation Reactions

• Ionic Compounds are Strong Electrolytes
  Determine charge on all ions of reactants
• Using Ion Charges Predict formula of products. (
  ion of one reactant forms compound with ion
  of other reactant)
• Balance Equation
• Determine if product is solid or aqueous solution

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Predicting Products of Precipitation Reactions
(cont.)

• Determine spectator ions (Ions that are still
  dissolved in water in the product)
• Write net ionic equation (Only shows ions
  involved in forming solid)

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Solubility Rules for Common Ionic Compounds In
water at 250C
4.2
42
Solubility Rules

• 1. A salt is soluble in water if it contains any
  one of the following ions
• NH4 Li Na K or NO3-
• Examples
• soluble salts
• LiCl Na2SO4 KBr Ca(NO3)2

43
Cl- Salts

• 2. Salts with Cl- are soluble, but not if the
• positive ion is Ag, Pb2, or Hg22.
• Examples
• soluble not soluble(will not dissolve)
• MgCl2 AgCl
• PbCl2

44
SO42- Salts

• 3. Salts with SO42- are soluble, but not if the
  positive ion is Ba2, Pb2, Hg2 or Ca2.
• Examples
• soluble not soluble
• MgSO4 BaSO4
• PbSO4

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Other Salts

• 4. Most salts containing CO32-, PO43-, S2- and
  OH- are not soluble.
• Examples
• soluble not soluble
• Na2CO3 CaCO3
• K2S CuS

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Precipitation Reactions
Precipitate insoluble solid that separates from
solution
Pb(NO3)2 (aq) 2NaI (aq) PbI2 (s)
2NaNO3 (aq)
molecular equation
ionic equation
net ionic equation
Na and NO3- are spectator ions
4.2
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4.2
48
Acids and Bases
49
Acids
Have a sour taste. Vinegar owes its taste to
acetic acid. Citrus fruits contain citric acid.
React with certain metals to produce hydrogen gas.
React with carbonates and bicarbonates to produce
carbon dioxide gas
Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.
4.3
50
Arrhenius Acids and Bases

• Acids produce H in aqueous solutions
• water
• HCl H(aq) Cl- (aq)
• Bases produce OH- in aqueous solutions
• water
• NaOH Na(aq) OH- (aq)

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Brönsted-Lowry Acids

• Acids are hydrogen ion (H) donors
• Bases are hydrogen ion (H) acceptors
• HCl H2O H3O
  Cl-
• donor acceptor
  -

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NH3, A Bronsted-Lowry Base

• When NH3 reacts with water, most of the
  reactants remain dissolved as molecules, but a
  few NH3 reacts with water to form NH4 and
  hydroxide ion.
• NH3 H2O NH4(aq) OH-
  (aq)
• acceptor donor

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Monoprotic acids Produce one H when dissolved
in water
Strong electrolyte, strong acid
Diprotic acids Produce two H when dissolved
in water
Strong electrolyte, strong acid
Triprotic acids Produce three H when dissolved
in water
Weak electrolyte, weak acid
4.3
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Strengths of Acids and Bases

• Strong acids completely ionize (100) in
  aqueous solutions
• HCl H2O H3O Cl- (100 ions)
• Strong bases completely (100) dissociate into
  ions in aqueous solutions.
• NaOH Na (aq) OH-(aq)
• (100 ions)

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Strong and Weak Acids and Bases

• Strong acids
• HCl, HNO3 , H2SO4
• Most other acids are weak.
• Strong bases
• NaOH, KOH, and Ca(OH)2
• Most other bases are weak.

57
Learning Check SW1

• Identify each of the following as a
• 1) strong acid or base 2) weak acid
• 3) weak base
• A. ___ HCl (aq)
• B. ___ NH3(aq)
• C. ___ NaOH (aq)
• D. ___ H2CO3 (aq)

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Solution SW1

• Identify each of the following as a
• 1) strong acid or base 2) weak acid
• 3) weak base
• A. _1__ HCl (aq)
• B. _3__ NH3(aq)
• C. _1__ NaOH (aq)
• D. _2__ H2CO3 (aq)

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Some Common Acids

• HCl hydrochloric acid
• HNO3 nitric acid
• H3PO4 phosphoric acid
• H2SO4 sulfuric acid
• CH3COOH acetic acid

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Neutralization Reactions

• When acid and bases with equal amounts of
  hydrogen ion H and hydroxide ions OH- are mixed,
  the resulting solution is neutral.
• NaOH (aq) HCl(aq) NaCl H2O
• base acid salt water
• Ca(OH)2 2 HCl CaCl2 2H2O
• base acid salt water

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Neutralization

• H3O and OH- combine to produce water
• H3O OH- ??
  2 H2O
• from acid from base neutral
• Net ionic equation
• H OH- ??
  H2O

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Ionic Equations for Neutralization

• Write strong acids, bases, and salt as ions
• H Cl- Na OH- Na Cl- H2O
• Cross out matched ions
• H Cl- Na OH- Na Cl- H2O
• Write a net ionic reaction
• H OH- H2O

63
Balancing Neutralization Equations

• Write the equation for the neutralization
  between magnesium hydroxide and nitric acid.1.
  Write the formulas of the acid and base
• Mg(OH)2 HNO3
• 2. Balance to give equal OH- and H
• Mg(OH)2 2 HNO3

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• 3. Write the products
• Mg(OH)2 2HNO3 Mg(NO3)2 H2O
• salt water
• (metal and nonmetal)
• 4. Balance products
• Mg(OH)2 2 HNO3 Mg(NO3)2 2 H2O

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Acid Carbonate ? Salt CO2(g) H2O (l)

• Carbonate Contains
• (CO3)-2 or (HCO3)-
• Chalk Ca(CO3)

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Learning Check

• Select the correct group of coefficients for the
  following neutralization equations
• A. __ HCl __ Al(OH)3 __AlCl3
  __ H2O
• 1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1
  3
• B.__ Ba(OH)2 __H3PO4 __Ba3(PO4)2
  __ H2O
• 1) 3, 2, 2, 2 2) 3, 3, 1, 6 3) 2, 3,
  1, 6

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Solution

• A. 3HCl 1Al(OH)3 1AlCl3 3H2O
• B. 3Ba(OH)2 2H3PO4 1Ba3(PO4)2 6H2O

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Solution Stoichiometry
The concentration of a solution is the amount of
solute present in a given quantity of solvent or
solution.
M KI
M KI
4.5
69
4.5
70
Acid/Base Titrations

• Experimental technique that determines the
  concentration (in Molarity) of an acid (or base)
• This is based upon an acid/base neutralization
  reaction.
• ACID BASE ? SALT H2O
• Base (or acid) is added until there is the same
  amount (same moles) of base and acid.

71
Titrations
In a titration a solution of accurately known
concentration is added gradually added to another
solution of unknown concentration until the
chemical reaction between the two solutions is
complete.
Equivalence point the point at which the
reaction is complete
Indicator substance that changes color at (or
near) the equivalence point
Slowly add base to unknown acid UNTIL
the indicator changes color
4.7
72
Acid-Base Titrations
Base (OH)-
Acid Base ? Salt H2O
Acid H
Introductory Chemistry 2/e by N Tro, Prentice
Hall, 2006, pg 480
73
At the endpoint of an acid/base titration.

• Moles acid Moles base
• (MV)acid (MV)base (moles/L)(L)
• Note
• If solid moles mass/ mol wt.
• If aqueous solution moles MV

74
Learning Check

• Write a balanced equation and calculate the mL
  of 2.00 M H2SO4 required to neutralize 50.0 mL
  of 1.00 M KOH?
• ___H2SO4 ___KOH ___K2SO4 H2O
• 1) 12.5 mL 2) 50.0 mL 3) 200. mL

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Solution N3

• How many mL of 2.00 M H2SO4 are required to
  neutralize 50.0 mL of 1.00 M KOH?
• H2SO4 2KOH K2SO4 2H2O
• 0.0500 L x 1.00 mole KOH x 1 mole H2SO4 x
• 1 L 2 mole KOH
• 1 L x 1000 mL 12.5 mL
• 2 mole KOH 1 L

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Learning Check N4

• A 25 mL sample of phosphoric acid is neutralized
  by 40. mL of 1.5 M NaOH. What is the molarity of
  the phosphoric acid solution?
• 3NaOH H3PO4 Na3PO4 3H2O
• 1) 0.45 M 2) 0.80 M 3) 7.2 M

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Solution S4
3NaOH H3PO4 ? Na3PO4 3H2O

• 0.040 L x 1.5 mole NaOH x 1 mole H3PO4
• 1 L 3 mole NaOH
• x 1 0.80 mol/L 0.80
  M
• 0.025 L

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4.7
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Normality?

• Activity of solution
• Chemical equivalents (gram equivalent weight of
  substance to produce one mole of protons or base)
• Normality differs from molarity by an integer
  based on number of active species involved.
• N1V1 N2V2

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Oxidation-Reduction Reactions
(electron transfer reactions)
Oxidation half-reaction (lose e-)
Reduction half-reaction (gain e-)
4.4
81
4.4
82
Zn is the reducing agent
Zn is oxidized
Cu2 is reduced
Cu2 is the oxidizing agent
Ag is reduced
Ag is the oxidizing agent
4.4
83
Oxidation number
The charge the atom would have in a molecule (or
an ionic compound) if electrons were completely
transferred.

• Free elements (uncombined state) have an
  oxidation number of zero.

Na, Be, K, Pb, H2, O2, P4 0

• In monatomic ions, the oxidation number is equal
  to the charge on the ion.

Li, Li 1 Fe3, Fe 3 O2-, O -2

• The oxidation number of oxygen is usually 2. In
  H2O2 and O22- it is 1.

4.4
84

• The oxidation number of hydrogen is 1 except
  when it is bonded to metals in binary compounds.
  In these cases, its oxidation number is 1.

• Group IA metals are 1, IIA metals are 2 and
  fluorine is always 1.

6. The sum of the oxidation numbers of all the
atoms in a molecule or ion is equal to the charge
on the molecule or ion.
7. Oxidation numbers do not have to be integers.
Oxidation number of oxygen in the superoxide ion,
O2-, is -½.
HCO3-
O -2
H 1
3x(-2) 1 ? -1
C 4
4.4
85
The oxidation numbers of elements in their
compounds
4.4
86
IF7
F -1
7x(-1) ? 0
I 7
K2Cr2O7
NaIO3
O -2
O -2
K 1
Na 1
3x(-2) 1 ? 0
7x(-2) 2x(1) 2x(?) 0
I 5
Cr 6
4.4
87
Types of Oxidation-Reduction Reactions
Combination Reaction
0
0
3
-1
Decomposition Reaction
1
5
-2
1
-1
0
4.4
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Types of Oxidation-Reduction Reactions
Combustion Reaction
0
0
4
-2
0
0
2
-2
4.4
89
Types of Oxidation-Reduction Reactions
Displacement Reaction
0
1
2
0
Hydrogen Displacement
0
4
0
2
Metal Displacement
0
-1
-1
0
Halogen Displacement
4.4
90
Types of Oxidation-Reduction Reactions
Disproportionation Reaction
Element is simultaneously oxidized and reduced.
1
-1
0
4.4
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The Activity Series for Metals
Hydrogen Displacement Reaction
M is metal BC is acid or H2O B is H2
4.4
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The Activity Series for Halogens
F2 gt Cl2 gt Br2 gt I2
Halogen Displacement Reaction
0
-1
-1
0
4.4
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Precipitation
Acid-Base
Redox (H2 Displacement)
Redox (Combination)
4.4
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Chemistry in Action Breath Analyzer
6
3
3CH3COOH 2Cr2(SO4)3 2K2SO4 11H2O
4.4
95
Solution Stoichiometry
The concentration of a solution is the amount of
solute present in a given quantity of solvent or
solution.
M KI
Mol.Wt. KI
500. mL
232 g KI
4.5
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4.5
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Dilution is the procedure for preparing a less
concentrated solution from a more concentrated
solution.
4.5
99
MiVi MfVf
Mi 4.00
Mf 0.200
Vf 0.06 L
Vi ? L
0.003 L 3 mL
3 mL of acid
57 mL of water
60 mL of solution
4.5
100
How to determine the concentration of a species
in an unknown
101
Gravimetric Analysis

• Dissolve unknown substance in water
• React unknown with known substance to form a
  precipitate
• Filter and dry precipitate
• Weigh precipitate
• Use chemical formula and mass of precipitate to
  determine amount of unknown ion

4.6
102
Titrations
In a titration a solution of accurately known
concentration is added gradually added to another
solution of unknown concentration until the
chemical reaction between the two solutions is
complete.
Equivalence point the point at which the
reaction is complete
Indicator substance that changes color at (or
near) the equivalence point
Slowly add base to unknown acid UNTIL
the indicator changes color
4.7
103

• End of Chapter 4

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Chemistry in Action Metals from the Sea
105
Chapter 9Acids and Bases

• Ionization of Water
• The pH Scale

106
Ionization of Water

• Occasionally, in water, a H is transferred
  between H2O molecules
• . . . . . .
  . .
• HO OH HOH OH-
• . . . . . .
  . .
• H H H
• water molecules hydronium hydroxide
  ion () ion (-)

107
Pure Water is Neutral

• Pure water contains small, but equal amounts of
  ions H3O and OH-
• H2O H2O H3O OH-
• hydronium hydroxide ion
  ion
• 1 x 10-7 M 1 x 10-7 M

H3O
OH-
108
Ion Product of Water Kw

• Molar concentration
• Kw H3O OH-
• 1 x 10-7 1 x 10-7
• 1 x 10-14

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Acids

• Increase H
• HCl (g) H2O (l) H3O (aq) Cl- (aq)
• More H3O than water gt 1 x 10-7M
• As H3O increases, OH- decreases
• H3O gt OH-

H3O
OH-
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Bases

• Increase the hydroxide ions (OH-)
• H2O
• NaOH (s) Na(aq) OH- (aq)
• More OH- than water, OH- gt 1 x 10-7M
• When OH- increases, H3O decreases
• OH? gt H3O

OH-
H3O
111
Using Kw

• The OH- of a solution is 1.0 x 10- 3 M. What
  is the H3O?
• Kw H3O OH- 1.0 x 10-14
• H3O 1.0 x 10-14
• OH-
• H3O 1.0 x 10-14 1.0 x 10-11 M
• 1.0 x 10- 3

112
Learning Check pH1

• The H3O of lemon juice is 1.0 x 10-3 M. What
  is the OH- of the solution?
• 1) 1.0 x 103 M
• 2) 1.0 x 10-11 M
• 3) 1.0 x 1011 M

113
Solution pH1

• The H3O of lemon juice is 1.0 x 10- 3 M.
  What is the OH-?
• OH- 1.0 x 10 -14 1.0 x 10-11 M
• 1.0 x 10 - 3

114
Using the Calculator

• 1.0 x 10 -14
• 4.0 x 10-5
• Enter 1.0 EE /- 14 ?? 4.0 EE /- 5
  
• 2.5 x 10 -10

115
Learning Check pH2

• The OH- of a solution is 5 x 10 -5 M. What is
  the H3O of the solution?
• 1) 2 x 10- 5 M
• 2) 1 x 1010 M
• 3) 2 x 10-10 M

116
Solution pH2

• The OH- of a water solution is 5 x 10-5 M.
  What is the H3O in the solution?
• H3O 1.0 x 10 -14
• 5 x 10- 5
• On some calculators
• 1.0 EE /- 14 ? 5 EE /- 5 2 x 10 -10
  M

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Learning Check pH3

• A.The OH- when H3O of 1 x 10- 4 M
• 1) 1 x 10-6 M
• 2) 1 x 10-8 M
• 3) 1 x 10-10 M
• B.The H3O when OH- of 5 x 10-9 M
• 1) 1 x 10- 6 M
• 2) 2 x 10- 6 M
• 3) 2 x 10-7 M

118
Solution pH3

• Kw H3O OH- 1.0 x 10 14
• A. (3) OH- 1.0 x 10 -14 1.0 x 10
  -10
• 1.0 x 10- 4
• B. (2) H3O 1.0 x 10 -14 2 x 10 - 6
• 5 x 10- 9

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pH

• Indicates the acidity H3O of the solution
• pH - log H3O
• From the French pouvoir hydrogene
• (hydrogen power or power of
• hydrogen)

120
pH

• In the expression for H3O
• 1 x 10-exponent
• the exponent pH
• H3O 1 x 10-pH M

121
pH Range

• 0 1 2 3 4 5 6 7 8 9 10 11 12
  13 14
• Neutral
• HgtOH- H OH-
  OH-gtH

Acidic
Basic
122
Some H3O and pH

• H3O pH
• 1 x 10-5 M 5
• 1 x 10-9 M 9
• 1 x 10-11 M 11

123
pH of Some Common Acids

• gastric juice 1.0
• lemon juice 2.3
• vinegar 2.8
• orange juice 3.5
• coffee 5.0
• milk 6.6

124
pH of Some Common Bases

• blood 7.4
• tears 7.4
• seawater 8.4
• milk of magnesia 10.6
• household ammonia 11.0

125
Learning Check pH4

• A. The H3O of tomato juice is 1 x 10-4 M.
• What is the pH of the solution?
• 1) - 4 2) 4 3) 8
• B. The OH- of an ammonia solution is
• 1 x 10-3 M. What is the pH of the solution?
• 1) 3 2) 11 3) -11

126
Solution pH4

• A. pH - log 1 x 10-4 -(- 4) 4
• B. H3O 1 x 10-11
• pH - log 1 x 10- 11 -(- 11) 11

127
Learning Check pH5

• The pH of a soap is 10. What is the H3O of
  the soap solution?
• 1) 1 x 10 - 4 M
• 2) 1 x 1010 M
• 3) 1 x 10 - 10 M

128
Solution pH5

• The pH of a soap is 10. What is the H3O of
  the soap solution?
• H3O 1 x 10-pH M
• 1 x 10-10 M

129
pH on the Calculator

• H3O is 4.5 x 10-6 M
• pH 4.5 x EXP(or EE) 6/- LOG /-
• 5.35

130
Learning Check pH6

• A soap solution has a H3O 2 x 10-8 M. What
  is the pH of the solution?
• 1) 8
• 2) 7.7
• 3) 6

131
Solution pH6

• A soap solution has a H3O 2.0 x 10-8 M.
  What is the pH of the solution?
• B) 2.0 EE 8 /- LOG /- 7.7

132
Learning Check pH7

• Identify each solution as
• 1. acidic 2. basic 3. neutral
• A. _____ HCl with a pH 1.5
• B. _____ Pancreatic fluid H 1 x 10-8 M
• C. _____ Sprite soft drink pH 3.0
• D. _____ pH 7.0
• E. _____ OH- 3 x 10-10 M
• F. _____ H 5 x 10-12

133
Solution pH7

• Identify each solution as
• 1. acidic 2. basic 3. neutral
• A. _1__ HCl with a pH 1.5
• B. _2__ Pancreatic fluid H 1 x 10-8 M
• C. _1__ Sprite soft drink pH 3.0
• D. _3__ pH 7.0
• E. _1__ OH- 3 x 10-10 M
• F. _2__ H 5 x 10-12

134
Acid Rain

• Unpolluted rain has a pH of 5.6
• Rain with a pH below 5.6 is acid rain
• CO2 in the air forms carbonic acid
• CO2 H2O H2CO3
• Adds to H of rain
• H2CO3 H (aq) HCO3-(aq)
• Formation of acid rain
• 1. Emission of sulfur and nitrogen oxides from
  the burning of fuels expecially coal with high S
  content, power stations, oil refineries,
  vehicles as well as bacterial decomposition, and
  lighting hitting N2
• SO2 26 million tons in 1980
• NO and NO2 22 million tons in 1980
• Mt. St Helens (1980) 400,000 tons SO2
• 2. Reactions in the atmosphere form SO3
• 2SO2 O2 ?? 2 SO3
• 3. Reactions with atmosphere water form acids

135
Sources of Acid Rain

• Power stations
• Oil refineries
• Coal with high S content
• Car and truck emissions
• Bacterial decomposition, and lighting hitting N2

136

• SO2 26 million tons in 1980
• NO and NO2 22 million tons in 1980
• Mt. St Helens (1980) 400,000 tons SO2
• Reactions with oxygen in air form SO3
• 2SO2 O2 2 SO3
• Reactions with water in air form acids
• SO3 H2O H2SO4 sulfuric acid
• NO H2O HNO2 nitrous acid
• HNO2 H2O HNO3 nitric acid

137
Effects of Acid Rain

• Leaches Al from soil, which kills fish
• Fish kills in spring from runoff due to
  accumulation of large amounts of acid in snow
• Dissolves waxy coatings that protect leaves from
  bacteria
• Corrodes metals, textiles, paper and leather

138
Antacids

• Used to neutralize stomach acid (HCl)
• Many contain one or more weak bases
• Alka-Seltzer NaHCO3, citric acid, and aspirin
• Di-gel CaCO3 and Mg(OH)2
• Gelusil Al(OH)3 and Mg(OH)2
• Maalox Al(OH)3 and Mg(OH)2
• Mylanta Al(OH)3 and Mg(OH)2

139
More Antacids

• Milk of Magnesia Mg(OH)2
• Rolaids AlNa(OH)2CO3
• aluminum sodium dihydroxy carbonate
• Tums CaCO3
• Tempo CaCO3, Al(OH)3, Mg(OH)2

140
Dilutions

• Add water
• Volume increases.
• New concentration is less than initial

141
Concentration of A Diluted Solution

• A 25 mL sample of a 6.0 M KOH is diluted by
  adding 75 mL of water. Calculate the new
  concentration of the KOH solution.
• Moles KOH 0.025 L x 6.0 moles 0.15 moles
• 1 L
• New volume 25 mL 75 mL 100. mL 0.100 L
• New molarity 0.15 moles 1.5 M
• 0.100 L

142
Learning Check SW 2

• A 125 mL sample of a 3.0 M HCl is diluted by
  adding 250 mL of water. The new concentration
  of the HCl solution is
• 1) 8.0 M
• 2) 1.5 M
• 3) 1.0 M

143
Solution SW 2

• 3) 1.0 M
• moles HCl 0.250 L x 3.0 moles 0.75 mole
• 1 L
• new M 0.75 mole 1.0 M HCl
• 0.750 L
• (new volume)

144
Learning Check SW 3

• A 50.0 mL sample of 15 sucrose solution is
  diluted by adding 200. mL of water. The new
  concentration of the sucrose solution is
• 1) 3.0
• 2) 7.5
• 3) 10.

145
Learning Check SW 3

• A 50.0 mL sample of 15 sucrose solution is
  diluted by adding 200. mL of water. The new
  concentration of the sucrose solution is
• 1) 3.0
• g sucrose 50.0 mL x 15 g sucrose 7.5 g
• 100 mL
• new 7.5 g sucrose 3.0
  sucrose
• 250 mL
• (new volume)