Acids and Bases

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Chapter 7

• Acids and Bases

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Homework Chapter 7

• Text Pages 206 to 209 1, 5 7, 10, 17, 18,
• 32, 37 39, 41, 43, 44, 49, 53 59, 61
• Blackboard Quiz

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I. IntroductionNote H moles/L of H

• Acids and Bases One Definition Arrhenius
  Definition
• Acid A substance which increases H or H3O
  when dissolved in water.
• Base A substance which increases OH- when
  dissolved in water.
• Note I will use H in place of the more correct
  H3O

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I. Introduction Examples Names to Learn

• Acids Bases
• HCl Hydrochloric Acid NaOH Sodium
  Hydroxide
• H2SO4 Sulfuric Acid KOH Potassium
  Hydroxide
• HNO3 Nitric Acid NaHCO3 Sodium Hydrogen
• HClO4 Perchloric Acid Carbonate
• HF Hydrofluoric Acid NH4OH Ammonium
  Hydroxide
• HC2H3O2 Acetic Acid (NH3 in H2O)

Only this H is acidic
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II. Acid Base Strengths

• Strong acids completely ionize in water to
  release H and an anion
• Weak acids only partially ionize in water.
• Examples (Strong) HClO4 H2SO4 HI HBr
  HCl HNO3
• HI -----) H I- (100 to products)
• Examples (Weak) HC2H3O2 HF, HCN
  (very toxic volatile)
• HF (-----) H F- (Less than 2 to
  products)
• Notes 1) Use caution with HClO4 and HNO3.
  They can react explosively with organics.
• 2) Strong acids can react quickly with
  proteins and triglyceride fats so, be
  careful in using them.

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II. Acid Base Strengths

• Strong bases completely ionize in water to
  release OH- and a cation weak bases only
  partially ionize in water.
• Examples (Strong) NaOH, KOH, Ba(OH)2
• NaOH -----) Na OH- (100 to products)
• Examples (Weak) NH4OH (NH3 in H2O), NaHCO3
• NH4OH (-----) NH4 OH- (Less than 2 to
  products)
• Notes 1) Bases react more quickly than acids
  with proteins and triglyceride fats so, be very
  careful in using them.
• 2) Bases feel slippery on touch. Why?

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III. Acid Base Reactions

• Acids rapidly react with bases to yield a salt
  plus H2O plus heat.
• Example HCl KOH ----) KCl H2O 14
  kcal/mole
• Heart of the reaction is H OH- ------) H2O
• We can quantitatively mix the acids bases
  together in a titration using a buret.

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Known M base. Add until acid neutalized (use
indicator) and then know mL added. Now can
calculate moles of base added from M m/L.
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IV. Measuring Acid Concentration

• - H and OH- are in dynamic equilibria in water.
  If you change the concentration of one, then the
  concentration of the other is also altered.
• H2O (------) H OH-
• - M of H or OH- is 1.0x10-7 m/L in pure
  water
• - If H 1.0x10-7 M - the solution is
  Neutral
• - If H gt 1.0x10-7 M - the solution is
  Acidic
• - If H lt 1.0x10-7 M - the solution is Basic
• - How do we measure acidity? Two common ways.

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IV. Measuring the Amount of Acid - Two Ways M
of H pH

• 1) M of H A vinegar solution has 2.0x10-4
  moles of H in 2.0 L. How acidic is it?
• M H 2.0x10-4 m 1.0x10-4 M H
• 2.0 L
• 2) pH - pH - Log H pH is a condensed log
  scale
• - Note Log 10x x - Log 10-x x
• - Examples
• a) What is the pH of the above vinegar solution.
  
• pH - Log 1.0x10-4 4
• b) What is the H if pH 9 H 1.0x10-9

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IV. Measuring Acid Concentration

• M Scale Acidic Neutral Basic
• 10-1 10-7 ..... 10-14
• pH Scale 1 .. 7 .. 14
• pH lt 7 (acidic) pH 7 (neutral)
  pH gt 7 (basic)

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IV. Measuring Acid ConcentrationCan Measure pH
with

• 1) pH probe and meter the probe generates
  electrical potential proportionate to H and
  meter records it. Must calibrate will give pH
  to within 0.01 pH units.

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IV. Measuring Acid ConcentrationCan Measure pH
with

• 2) Indicators organic compounds whose color
  varies with acidity. Can coat paper with several
  indicators and specific color will tell pH to
  within 1 pH.

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V. Buffers

• Buffer a mixture of a weak acid and its salt
  which resists a change in pH. The weak acid and
  its salt will consume strong acids or bases.
• Examples
• 1) A drop of HCl in 1 mL of water will change the
  pH from 7 to 1 a drop of NaOH in 1 mL of water
  will change the pH from 7 to 13. Water is not a
  buffer.
• 2) Add a drop of either HCl or NaOH to 1 mL of
  blood, and the pH changes less than 0.1. Blood
  is a buffer.
• 3) Add a drop of either HCl or NaOH to a mixture
  of HF NaF and the pH stays at 3.2. This is a
  buffer.