Acid-Base Behavior

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Acid-Base Behavior
Acids Bases
Taste sour Taste Bitter
Burn Skin Burn Skin/Feel Slippery
Turn Litmus Red Turn Litmus Blue
Dissolve metals
Citrus fruit Vitamin C (Ascorbic Acid) Vinegar Battery Acid Soap Ammonia Baking Soda Tums Drano
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Definitions of Acids/Bases

1. Arrhenius
2. Bronsted/Lowry
3. Lewis

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Arrhenius Definition

• Acids Produce H3O (H) in water
• Bases Produce OH- in water
• Examples
• HCl H2O ?
• HNO3 H2O ?
• HClO4 H2O ?

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Arrhenius Definition

• HBr H2O ?
• NaOH ?
• KOH ?
• Ba(OH)2 ?
• D. H3O - hydronium ion

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Arrhenius Definition
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Bronsted-Lowry Definition

1. Acid H (proton) donor
2. Base - H (proton) acceptor
3. Works even if water is not present

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Bronsted-Lowry Definition
D. Examples HCl H2O ? NH3 H2O
? HC2H3O2 H2O ? OCl- H2O ?
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Bronsted-Lowry Definition
NH3 H2PO4- ?NH4 HPO42- What is the
conjugate base of HClO4 H2S PH4 HCO3- What
is the conjugate acid of CN- SO42- H2O HCO
3- E. Amphiprotic acts as either an acid or
base (H2O)
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Water and Kw

• Autoionization of H2O
• 2H2O(l) ? H3O(aq) OH-(aq)
• Kw H3OOH-/H2O2
• Kw H3OOH-
• Kw 1 X 10-14

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Kw and pH

• 1. Kw H3OOH- All aqueous solns contain
  BOTH H3O and OH-.
• Acidic solns contain more H3O(hydronium ion)
• Basic solns contain more OH- (hydroxide)
• Neutral solution H3O OH-

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Kw and pH
H3O OH- A/B?
2 X 10-5
2.5 X 10-6
3 X 10-9
4.8 X 10-8
100X OH-
Neutral
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pH

• Measure of acidity/basicity(alkalinity)
• 0-6.99 Acidic
• 7 Neutral
• 7.01 14 Basic/Alkaline
• Logarithmic Scale
• pH 2 H3O 0.01 M
• pH 1 H3O 0.1 M

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pH

1. Each change in pH is a factor of 10 (Richter
   scale is also logarithmic)
2. Indicators

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pH

• 13 Oven Cleaner/Drano
• 12 Hair remover
• Ammonia
• Soap
• Baking Soda, bleach, antacids
• Shampoo
• Water, blood, eggs, baby shampoo

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pH

• 6 Urine, milk, saliva
• Coffee, bread, rainwater
• Tomatoes
• Vinegar, soda, beer
• Stomach acid, lemon juice
• 1 Battery acid

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pH Formula

• pH -log H3O
• Examples
• What is the pH if the H3O of a solution is 1
  X 10-12?
• What is the pH if the H3O of a solution is
  5.0 X 10-6? (5.3)

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pH Formula

• What is the H3O of a solution if the pH
  3.76?
• What is the H3O of a solution if the pH
  9.18?
• pOH -log OH- pH -log H3O
• pH pOH 14 Kw H30OH-

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pH Formula

• H3O OH-
• pH pOH

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pH Formula
H3O OH- pH pOH A or B
7 X 10-10
6 X 10-10
9.4
5.2
8.7
6.2
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Strong Acids

• Completely (100) dissociates in water
• Low pH and no Ka, single arrow
• Common Strong Acids
• HCl HBr HI
• HNO3
• H2SO4
• HClO4

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Strong Acids

• Eqn/Species
• HCl H2O ?
• HNO3 H2O ?
• H2SO4 H2O ?
• (just one proton)

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Strong Acids

• 1. What is the pH of 0.040 M HCl? (Ans 1.40)
• 2. What is the pH of 0.0040 M HNO3? (Ans 2.40)

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Strong Acids

• 3. A soln of HNO3 has a pH of 2.66. What is the
  conc. of the acid? (Ans 0.0022 M)
• 4. A soln of HBr has a pH of 3.55. What is the
  conc. of the acid? (Ans 0.000282 M)

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Strong Bases

1. Soluble Hydroxides. Completely (100) dissociate
   in water
2. High pH and no Kb

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Strong Bases

• 3. Common Strong Bases
• NaOH ?
• KOH ?
• Ba(OH)2 ?

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Strong Bases

1. What is the pH of 0.011 M NaOH? (Ans 12.0)
2. What is the pH of 0.011 M Ca(OH)2? (Ans 12.3)
3. What is the molarity of a soln of KOH that has a
   pH of 11.89? (Ans 0.007763)

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Weak Acids

• Do not completely dissociate in water. Higher
  pH.
• Equilibrium. Has a Ka
• Some Common Weak Acids
• HC2H3O2 Acetic
• H3PO4 Phosphoric
• H2CO3 Carbonic
• HC6H7O6 Ascorbic

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Weak Acids

• Eqn/Species/Ka
• HC2H3O2 H2O ?
• HNO2 H2O ?
• HSO4- H2O ?

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Weak Acids

• What is the pH of 0.100 M HC2H3O2? (Ans 2.9)
• 2. What is the pH of 0.100 M HC3H5O3? (Ans
  2.4)
• The larger the Ka, the stronger the acid.

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Weak Acids

• What is the Ka of HCN if a 0.20 M soln has a pH
  of 5.00? (Ans 5.0 X 10-10)
• 4. What is the Ka of HF if a 0.10 M soln has a
  pH of 2.1? (Ans6.8 X 10-4)

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• We buy a gallon of vinegar (acetic acid) and find
  the pH to be 3.74.
• Calculate the molarity of the acid. (0.00202 M)
• Calculate the grams of acetic acid present in 1
  quart of vinegar (1 L 1.0567 qt). (0.115)
• Calculate the pH of 0.0200 M acetic acid. (3.2)
• Draw a Lewis Dot structure of acetic acid
  (CH3COOH, both oxygens bonded to the second
  carbon).
• State the hybridization of each carbon.

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• A 0.0987 M solution of citric acid is prepared.
• Calculate the pH of the solution. (2.07)
• Calculate the OH- concentration. (1.17 X10-12)
• Experimentally, the pH is measured to be 2.3.
  Using only the pH and the starting molarity
  (0.0987 M), calculate Ka. (2.68 X 10-4)
• Calculate the percent error for Ka. (64)
• List the species that would be present in the
  solution, indicating the major species.

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Weak Acids

• Ionization H3O X 100
• acid
• 6. What is the percent ionization of a 0.10 M
  solution of HCHO2 ? (Ans 4.2)

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Weak Acids

• 7. What is the percent ionization of a 0.020 M
  solution of niacin, HC6H4NO2? The Ka for Niacin
  is 1.5 X 10-5. (Ans 2.7)
• 8. What is the Ka of HC2H3O2 if a 0.30 M
  solution is 0.77 ionized? (Ans Ka 1.8 X
  10-5)

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• The following questions refer to the weak acid HF
  (Ka 6.8 X 10-4)
• Calculate the pH and moles of F- in 0.400L of
  0.400M HF. (1.8, 6.6 X 10-3 moles)
• Calculate the percent ionization for the previous
  problem. (4.1)
• Would the major species be HF or F-?
• The ionization of a new fluorine containing
  acid (0.200M) is 0.56. Calculate the Ka (6.3 X
  10-6 )
• Why is HF unique among the binary
  halogen-containing acids?

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pH and Concentration

• pH depends on
• a. Strength of the acid
• b. Concentration (molarity)
• Show pH from 1 14 (Strong, weak and dilute)
• 2. Example
• 0.1 M HCl pH 1
• 0.1 M HC2H3O2 pH 2.8
• 0.0016 M HCl pH 2.8

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Acid Review

• Write the eqns for the dissociation of the
  following. Indicate all species and write Ka if
  needed
• HNO3
• HNO2
• HC7H5O2
• HBr

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Weak Bases

• Do not produce a high concentration of OH- with
  water
• Ammonia and Ammonia Derivatives (Amines)
• NH3 (CH3)2NH
• CH3NH2 (CH3)3N
• C5H5N

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• NH3 H2O ?
• CH3NH2 H2O ?
• (CH3)2NH H2O ?
• (CH3)3N H2O ?

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Weak Bases

• What is the pH of 0.100 M NH3? (Ans 11.1)
• What is the pH of 0.0100 M C5H5N? (Ans 8.6)
• 3. A soln of NH3 has a pH of 10.5. What is the
  molarity? (Ans 0.00587 M)

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Review

• Write the eqns for the dissociation of the
  following. Indicate all species and write Ka or
  Kb if needed
• Ca(OH)2
• HC7H5O2
• HCl
• C2H5NH2

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Salts

• Finding Kb from Ka
• HF H2O ?
• What is Ka for the NH4 ion? (Ans 5.6 X 10-10)

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Salts of Weak Bases

• Tend to be positive ions
• Salts of Weak Bases act as acids
• Forming Salts
• WB CA Salt
• NH3
• CH3NH2
• C6H5NH2

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Salts of Weak Bases

• NH4Cl H2O ?
• CH3NH3Br H2O ?
• C5H5NHNO3 H2O ?
• NH4NO3 H2O ?

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Salts of Weak Acids

• Tend to be negative ions
• Salts of Weak Acids act as bases
• Forming Salts
• WA CB Salt
• HC2H3O2
• HC3H5O2
• HNO2
• HF

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Salts of Weak Acids

• NaClO H2O ?
• NaF H2O ?
• Ca(NO2)2 H2O ?

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Salts and pH

1. What is the pH of 0.010 M NaC2H3O2? (Ans 8.4)
2. What is the pH of 0.010 M NaF? (Ans 7.6)
3. What is the pH of 0.010 M NH4Cl? (Ans 5.6)

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• What is the pH of 0.010 M (CH3)2NH2Br? (Ans
  6.4)
• If the pH of a soln of NaC2H3O2 is 7.4, what is
  the concentration? (Ans 0.00011 M)
• If the pH of a soln of C5H5NHNO3 is 3.6, what is
  the molarity? (Ans 0.011 M)
• If the pH of C2H5NH3Cl is 6.2, what is the
  molarity? (Ans 0.026 M)

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Review

• Write the eqns for the dissociation of the
  following. Indicate all species and write Ka or
  Kb if needed
• NaOH NaC3H5O3
• HC7H5O2 C2H5NH3NO3
• C2H5NH2 HBr

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• A solution of HClO is tested and the pH is found
  to be 4.29
• Calculate the concentration of HClO in the
  solution. (0.0877 M)
• Would HClO or ClO- be greater at equilibrium?
  Justify your prediction.
• NaOH is added to the solution of HClO. Write the
  reaction that occurs. (Assume the proper ratios
  are used).
• Water is allowed to evaporate from the solution.
  What compound is present?
• Calculate how many grams of NaClO must be added
  to make 2.00 L of a solution with a pH of 10.50.
  (Ans 44.7g)

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Polyprotic Acids

• Polyprotic Acids Acids that can donate more
  than one H
• Important Examples
• H2SO4 - Sulfuric
• H3PO4 - Phosphoric
• H2CO3 Carbonic
• 3. Much less likely to give away 2nd and 3rd H
  ions

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Polyprotic Acids

• H2CO3 ? HCO3- ? CO32-

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Polyprotic Acids

• Will Na2HPO4 act as an acid or a base in water
  (Identify parent acid)
• Will K2HC6H5O7 act as an acid or a base in water?

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Polyprotic Acids

• Will the following act as acids or bases in
  water
• KHS
• Na2HAsO4
• K3C6H5O7
• Na3PO4 (Calculate/estimate pH, 0.100 M)

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Polyprotic Acids

• What is the pH of 0.0037 M H2CO3? (Ans 4.40)
• You generally do NOT have to consider the second
  or third H for the pH

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Carboxylic Acids

• Carboxyl Group
• Examples
• HCO2H Formic Acid
• HC7H4O2 Benzoic Acid
• HC2H3O2 Acetic
• (CH3CO2H)
• (CH3COOH)

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Amino Acids
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Amino Acids

• Glycine

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Amino Acids

• 20 Amino Acids (8 essential, 10 in children)
• Diglycine
• Aspartame (Aspartic acid/ Phenylalanine)
• Sickle Cell Anemia
• -208 AA protein (1 wrong)
• -Mutation to help malaria survival rate
• -Sickle Cell Red Blood Cell

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Strengths of Binary Acids

• Acidity increases as you go across
• More electronegativity difference
• Bond polarity increase
• Strength increases as you go down
• H-X bond strength decreases with size of X
• X cant hold H as well.

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Strengths of Oxyacids

• More electronegative pull makes it more acidic
• HClO
• Ka 3.0 X 10-8
• HIO
• Ka 2.3 X 10-11

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Strengths of Oxyacids

• More oxygens pull on the Hs electrons more.
  More acidic.

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• Hypochlorous H O Cl Ka 3.0 X 10-8
• (HClO)
• Chlorous H O Cl O Ka 1.2 X 10-2
• (HClO2)
• O
• Chloric H O Cl O Strong Acid
• (HClO3) O
• Perchloric H O Cl O Strong Acid
• O
• (HClO4)

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• Illustrate how two amino acids form a dipeptide.
  Be sure to include the byproduct of the reaction
• Why is perchloric acid (HClO4) a strong acid
  while hypochlorous acid (HClO) is a weak acid?
  Draw structures to support you answer.
• Is the oxalate ion, C2O4-2 a weaker or stronger
  base than methylamine, CH3NH2? Show all equations
  and math.

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Lewis Acids and Bases

• Lewis Acid Electron Pair Acceptor
• Lewis Base Electron Pair Donor

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• Coordination Complexes (transition metals)
• Ni2 6NH3 ? Ni(NH3)62
• Co2 6NH3 ? Co(NH3)62

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1. How much more 0.012 M NaOH does it take to
   neutralize a solution of HCl that is pH2
   compared to one that is pH 4?
2. Is 0.012 M NaOH an appropriate concentration to
   use for both pH values? Suggest any changes you
   might want to make.

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• pH 2 HCl 0.01 M
• Pretend 1 L of HCl
• Need 833 mL of NaOH
• pH 4 HCl 0.0001 M
• Pretend 1 L of HCl
• Need 8.33 mL of NaOH
• 0.012 M is NOT appropriate for pH 4. Use a a
  more dilute solution.

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• Which is more acidic a 0.001 M solution of HCl
  or a solution of a weak acid with a pH of 2.32?
• The volume of an adult stomach is 450 mL. If the
  pH is 2.0, how many moles of H3O are present in
  the stomach. Assume HCl is the only acid
  present.

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• NH4Cl
• Na2CO3
• KC2H3O2
• KCl
• NaH2PO4

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• Produces OH- and accepts a proton
• a) C6H5COO- PO43-
• b) HCO3- C2H5NH3
• a) A B CA CB
• b) A B CB CA
• c) B A CA CB
• 22. a) H2C6H7O5- H2O ?? H3C6H7O5 OH-
• H2C6H7O5- H2O ?? HC6H7O52- H3O
• b) H3C6H7O5 (CA) HC6H7O52- (CB)

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• 32.a) OH- 2.2 X 10-12 (acidic)
• b) OH- 6.7 X 10-6 (basic)
• c) OH- 3.2 X 10-8 (acidic)
• 38. a) H increases, OH- decreases b) pH
  12.1
• c) H3 X 10-7M, OH- 4 X 10-8M
• 40.

pH pOH H OH- A/B
11.25 2.75 5.6 X10-12 1.8 X10-3 B
7.98 6.02 1.1 X10-8 9.6 X10-7 B
3.36 10.64 4.4 X10-4 2.3 X10-11 A
11.93 2.07 1.2 X10-12 8.5 X10-3 B
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• H from 6 X10-6 to 3 X10-6
• OH- from 2 X10-9 to 4X10-9

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• A) Strong base completely dissociates
• b) 0.070 M OH-
• c) False
• 46. a) 2.87 b) 2.68 c) 2.00 d) 1.90
• 48. a) 12.91 b) 12.6 c) 10.6 d) 12.1
• 0.0056 M
• Ka 5.3 X 10-5
• 0.087 M, 0.0132M
• 2.1 X 10-4 mol HF (1.0 X 10-3 M HF)
• HClO 9.0 X 10-3 M

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• a) 4.27 b) 5.98 c) 9.51
• 2.59
• a) 0.721 b) 1.27 c) 2.55
• a) C3H7NH3 OH-
• b) H2PO4- OH-
• c) C6H5CO2H OH-
• OH- 1.5 X 10-3 M pH 11.17
• a) Kb 1.6 X 10-6 b) pKb 5.79

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• b) Kb 1.8 X 10-4 c) CO32- is stronger base
• 82. a) Ammonia b) Hydroxylammonium
• c) Ka NH4 5.6 X 10-6, HONH3 9.1X10-7
• a) pH 8.09 b) pH 12.54
• 88. KBr
• a) Cl more electronegative than S
• b) P is more electronegative than As
• c) More Os d) Parent acid e) More Os
• 96. a) NO2- b) PO43- c) CO32-

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Ka Kb
KH2AsO4 1 X 10-7 1.8 X 10-12
NaHCO3 5.6 X 10-11 2.3 X 10-8
NaH2C6H5O7 1.7 X 10-5 1.4 X 10-11
K2CO3 -- 1.8 X 10-4
Ca(HC2O4)2 6.4 X 10-5 1.7x10-13
Na2S --- 100,000
LiHC3H2O4 2 X 10-6 6.67 X 10-12
NaHSeO3 5.3 X 10-9 4.3X 10-12
KHS 1 X 10-19 1 X 10-7
KHC4H4O6 4.6 X 10-5 1 X 10-11