Warm Up

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Warm Up

• Pg 650 75

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Acids and Bases

• 14.1-14.4

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Models of Acids and Bases

• Arrhenius Concept Acids produce H in solution,
  bases produce OH? ion.
• Brønsted-Lowry Acids are H donors, bases are
  proton acceptors.
• HCl H2O ? Cl? H3O
• acid base

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Conjugate Acid/Base Pairs

• HA(aq) H2O(l) ? H3O(aq) A?(aq)
• conjugate conjugate
• acid 1 base 2 acid 2 base 1
• conjugate base everything that remains of the
  acid molecule after a proton is lost.
• conjugate acid formed when the proton is
  transferred to the base.
• Conjugate acid base pair two substances related
  to each other by the donating and accepting of a
  single proton.

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Acid Dissociation Constant (Ka)

• HA(aq) H2O(l) ? H3O(aq) A?(aq)
• The larger the Ka value the stronger the acid

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Acid Strength
Strong Acid

• Its equilibrium position lies far to the right.
  (HNO3, HCl, HBr, HI, H2SO4, HClO4, )
• Yields a weak conjugate base. (NO3?,Cl-, HSO4-,
  ClO4-)

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Strong Bases

• LiOH
• NaOH
• KOH
• RbOH
• Ca(OH)2
• Sr(OH)2
• Ba(OH)2

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Acid Strength(continued)
Weak Acid

• Its equilibrium lies far to the left. (CH3COOH)
• Yields a much stronger (it is relatively strong)
  conjugate base than water. (CH3COO?)

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Water as an Acid and a Base

• Water is amphoteric (it can behave either as an
  acid or a base).
• H2O H2O ? H3O OH?
• 
  conj conj
• acid 1 base 2 acid 2 base 1
• Kw 1 ? 10?14 at 25C

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The pH Scale

• pH ? ?logH
• pH in water ranges from 0 to 14.
• Kw 1.00 ? 10?14 H OH?
• pKw 14.00 pH pOH
• As pH rises, pOH falls (sum 14.00).

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Calculate H and OH- for a solution with 1 x
10-5 M OH-
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Calculate H and OH- for a solution with 1 x
10-7 M OH-
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Calculate H and OH- for a solution with 10 M
H
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Calculate pH and pOH for a solution that is
1x10-3M OH-
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Calculate pH and pOH for a solution that is 1M H
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Calculate the pOH, H, and OH- concentrations
for a sample that has a pH of 7.41
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Classwork

• Pg 704 33-45 odd

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Warm Up

• Calculate the H and OH- for the following
  solutions
• pH 7.4
• pOH 9.6

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Calculating the pH of Weak Acid Solutions

• 14.4-14.5

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Calculate the pH of .0001 M HCl
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Percent Dissociation (Ionization)
dissociation X / HA0
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Solving Weak Acid Equilibrium Problems

• List major species in solution.
• Choose species that can produce H and write
  reactions.
• Based on K values, decide on dominant
  equilibrium.
• Write equilibrium expression for dominant
  equilibrium.
• List initial concentrations in dominant
  equilibrium.

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Solving Weak Acid Equilibrium Problems (continued)

• Define change at equilibrium (as x).
• Write equilibrium concentrations in terms of x.
• Substitute equilibrium concentrations into
  equilibrium expression.
• Solve for x the easy way.
• Verify assumptions using 5 rule.
• Calculate H and pH.

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Calculate the pH of a .1 M aqueous solution of
hypochlorous acid HOCl, Ka3.5 x10-8
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List major speices

• HOCl and H2O

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Choose the species that can produce H and write
balanced equations for the reactions producing H
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Using the equilibrium constants decide which will
dominate the equlibrium.
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Write the equilibrium expression
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List the initial concentrations in a ice chart
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Define change
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Write the equilibrium concentrations
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Substitute equilibrium values into the
equilibrium expression
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Solve for x assuming that HA0 x HA0
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Check to see that your assumption was ok less
than 5
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Calculate the pH from the H concentration at
equilibrium.
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Calculate the pH of a solution that contains 1 M
HCN Ka6.2 x 10-10 and 5 M HNO2 Ka 4 x 10-4 .
Also calculate the concentration for the cyanide
ion in this solution at equilibrium.
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Percent Dissociation (Ionization)
dissociation X / HA0
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Calculate the percent dissociation of acetic acid
Ka 1.8x 10-5 for 1 M acetic acid
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Calculate the percent dissociation of acetic acid
Ka 1.8x 10-5 for 0.1 M acetic acid
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In a 0.1 M aqueous solution lactic acid(HC3H5O30)
is 3.7 percent dissociated. Calculate the Ka
value for lactic acid.
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Classwork

• Pg 705 47-69 odd

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Warm Up

• Calculate the pH of a .2 M solution of iodic acid
  (HIO3) Ka 0.17

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Bases

• 14.6

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Bases

• Strong and weak are used in the same sense
  for bases as for acids.
• strong complete dissociation (hydroxide ion
  supplied to solution)
• All hydroxides of group 1 are strong bases.
  Calcium, Barium and Strontium hydroxides are also
  strong
• NaOH(s) ? Na(aq) OH?(aq)

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Bases(continued)

• weak very little dissociation (or reaction with
  water)
• H3CNH2(aq) H2O(l) ? H3CNH3(aq) OH?(aq)

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Calculate the pH of 5 x 10-2 M NaOH solution
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Calculate the pH of a 15.0M solution of NH3 (Kb
1.8 x 10-5)
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Calculate the pH of a 1.0M solution of
methylamine CH3NH2 Kb 4.38 x 10-4
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Classwork

• Pg 705 71-91 odd

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Warm Up

• Calculate the pH of a .05 M (C2H5)2NH solution
  Kb 1.3 x 10 -3

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Polyprotic Acids

• 14.7

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Polyprotic Acids

• . . . can furnish more than one proton (H) to
  the solution.

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Calculate the pH of a 5 M H3PO4 solution and the
equilibrium concentrations of the species H3PO4,
H2PO4, HPO4 and PO4-.
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Sulfuric acid is unique because it is a strong
acid

• This means when you have dilute solutions you
  will have to use the both Ka values.

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Calculate the pH of a 1 M solution of sulfuric
acid
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Calculate the pH of a 1 x 10-2 M solution of
sulfuric acid
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Classwork

• Pg 706 93-97 odd

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Warm Up

• Calculate the pH of a 5 x 10-3 M solution of
  sulfuric acid.

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Salts as Acids and Bases

• 14.8

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Acid-Base Properties of Salts
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Ka and Kb

• Ka x Kb Kw
• This is helpful for calculating Ka and Kb for
  weak acids and bases.

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Calculate the pH of a .3 M solution of NaF. The
Ka value for HF is 7.2x10-4
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Calculate the pH of a .1 M NH4Clsolution. The Kb
for NH3 1.8x10-5
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Classwork

• Pg 707 99-111 odd

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Structure and Acid-Base Properties

• Two factors for acidity in binary compounds
• Bond Polarity (high is good)
• Bond Strength (low is good)

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Oxides

• Acidic Oxides (Acid Anhydrides)
• O?X bond is strong and covalent.
• SO2, NO2, CrO3
• Basic Oxides (Basic Anhydrides)
• O?X bond is ionic.
• K2O, CaO

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Lewis Acids and Bases

• Lewis Acid electron pair acceptor
• Lewis Base electron pair donor