Acids

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Acids Bases
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Naming Review
Binary Acids Start the acid name with hydro- Add the root of the second element with the suffix ic Add the word acid EX. HCl- hydrochloric acid Polyatomic Acids Use the root name of the polyatomic Add ic if the polyatomic ends in ate What I ATE was ICky Add ous if the polyatomic ends in ite I took a bITE it was deliciOUS Add the word acid
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Definitions

• Acids
• Ionize to form hydronium ions (H3O) in water
  (Arrhenius)
• Proton donor (Bronsted-Lowry)
• Electron-pair acceptor (Lewis)

HCl H2O ? H3O Cl
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Definitions

• Bases
• Dissociate or ionize to form hydroxide ions (OH-)
  in water (Arrhenius)
• Proton acceptor (Bronsted - Lowry)
• Electron-pair donor (Lewis)

NH3 H2O ? NH4 OH-
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Acid-Base Reactions

• Conjugate Base the species that remains after
  the acid has given up a proton
• Conjugate Acid the species that is formed when
  the base gains a proton

HCl H2O ? H3O Cl-
acid
conjugate base
conjugate acid
base
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Acid-Base Reactions

• HF H2O ? F- H3O

HF H2O H3O F-
Acid Base Conjugate Acid Conjugate Base
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Properties
ACIDS
BASES

• sour taste
• corrosive
• electrolytes
• turn litmus red
• react with metals to form H2 gas

• bitter taste
• corrosive
• electrolytes
• turn litmus blue
• slippery feel

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Uses
ACIDS

• H3PO4 - soft drinks, fertilizer, detergents
• H2SO4 - fertilizer, car batteries
• HCl - gastric juice
• HC2H3O2 - vinegar

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Uses
BASES

• NaOH - lye, drain and oven cleaner
• Mg(OH)2 - laxative, antacid
• NH3 - cleaners, fertilizer

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Strong vs. Weak

• Strong Acid/Base
• 100 ions in water completely dissociate
• strong electrolyte

• Weak Acid/Base
• few ions in water incomplete dissociation
• weak electrolyte

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Strong Acids

• H2SO4 Sulfuric Acid
• HClO4 Perchloric Acid
• HCl Hyrochloric Acid
• HNO3 Nitric Acid
• HBr Hydrobromic Acid
• HI Hydroidic Acid

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Strong Bases

• Ca(OH)2 Calcium hydroxide
• Sr(OH)2 Strontium hydroxide
• Ba(OH)2 Barium hydroxide
• NaOH Sodium hydroxide
• KOH Potassium hydroxide
• RbOH Rubidium hydroxide
• CsOH Cesium hydroxide

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pH Scale

• pH
• a measure of the concentration of H3O ions in
  solution
• measured with a pH meter or an indicator with a
  wide color range

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pH Scale

• pH of Common Substances

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ConcepTest

• Which of the following "molecular" pictures best
  represents a concentrated solution of the weak
  acid HA?

A
B
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Neutralization Reaction

• ACID BASE ? SALT WATER

HCl NaOH ? NaCl H2O
Neutralization does not always mean pH 7.
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Neutralization Reaction

• KOH HNO3 ? H2O KNO3

Acid? Base? Salt?
HNO3 KOH KNO3
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Indicators

• Indicator
• Substance that changes color in an acid or base
• Acid-base indicators are very weak acids and
  bases that change color when they
• accept a proton from acid
• donate one to a base

Indicator Color of acid Color of base
Litmus paper Red Blue
Phenolphthalein Colorless Pink
Goldenrod Yellow Red
Bromothymol blue Yellow Blue
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Titration

• The controlled addition and measurement of the
  amount of a solution of known concentration
  required to react completely with a measured
  amount of solution of unknown concentration
• Equivalence Point the point at which two
  solutions used in a titration are present in
  chemically equivalent amounts
• Occurs at a pH that is halfway between the two
  curves
• End Point the point at which an indicator
  changes color

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Titration
Notice the amount of titrating solution used
As soon the liquid in the beaker changes color,
stop the dropping.
Beaker vinegar phenolphthalein Buret sodium
hydroxide
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Titration Curves
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Titration Curves
strong acid / strong base
weak acid / strong base
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H2O Acid or Base?

• Amphoteric a species that can react as either
  an acid or a base

NH3 H2O ? NH4 OH-
base
acid
HCl H2O ? H3O Cl
acid
base
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Self-Ionization of H2O

• Two water molecules produce a hydronium ion and a
  hydroxide ion by transfer of a proton
• H2O H2O lt----gt H3O? OH?
• At 25 C the concentrations of H3O? OH? in
  pure water are 1.0x10-7M
• H3O? 1.0x10-7M OH? 1.0x10-7M
• Ionization constant of water is Kw
• Kw H3O? OH?
• Kw H3O? OH? (1.0x10-7M)(1.0x10-7M)
  1.0x10-14M2

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Ionization Problems

• A 1x10-4M solution of HNO3 has been prepared for
  a lab experiment.
• a. Calculate H3O?
• b. Calculate OH?

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pH Concentration

• pH of a solution is the negative of the common
  logarithm of the hydronium ion concentration
• pH -log H3O?
• neutral solution at 25C H3O? 1.0x10-7M
• pH -log (1.0x10-7) -(-7) 7
• pOH -log (1.0x10-7) -(-7) 7
• pH pOH 14
• Kw H3O? OH? 1.0x10-14M2
• -log(1.0x10-14) 14

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pH Conc. Calculations

1. What is the pH of a 1x10-3M NaOH solution?
2. What is the pH of a solution if the H3O? is
   3.4x10-5M?
3. Determine the hydronium ion of an aqueous
   solution that has a pH of 4.0

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pH Conc. Calculations

• The pH of a solution is measured and determined
  to be 7.52
• What is the hydronium ion concentration?
• What is the hydroxide ion concentration?
• Is the solution acidic or basic?