Chapter 9 Acids and Bases

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Chapter 9Acids and Bases

• Ionization of Water
• The pH Scale

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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 (-)

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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-
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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
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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

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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

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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

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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

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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

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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

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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)

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pH

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

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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
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Some H3O and pH

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

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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

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pH of Some Common Bases

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

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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

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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

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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

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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

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pH on the Calculator

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

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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

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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

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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

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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

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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

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Sources of Acid Rain

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

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• 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

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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