Day 1115

1
Day 11/15

• 45 Discuss HW, Labs, Tests
• 45 Quiz
• 60 Acids and Bases
• Lunch
• 30 IceBreaker/Prelabs
• 135 Labs

2
Acids, Bases, and Neutralization

• To insert your company logo on this slid
• From the Insert Menu
• Select Picture
• Locate your logo file
• Click OK
• To resize the logo
• Click anywhere inside the logo. The boxes that
  appear outside the logo are known as resize
  handles.
• Use these to resize the object.
• If you hold down the shift key before using the
  resize handles, you will maintain the proportions
  of the object you wish to resize.

• Mr. Chan
• Northwestern University

3
Properties of Acids and Bases

• Taste/Feel
• Ionize/Dissociate - Electrolytes
• pH
• Reactions with metals
• Reactions with indicators

4
Nomenclature of Acids and Bases

• Acid HX general form
• -ide (-ic), -ite (ous), -ate (ic)
• Bases generally contain hydroxide ions
• Examples
• H2S, H2SO3, H2SO4
• KOH, NH3
• nitric acid, carbonic acid
• calcium hydroxide, aluminum hydroxide

5
Classifying Acids, Bases, Neutral

• Hydronium and hydroxide ions
• H3O - water that gains a hyrdogen ion
• OH- - water that loses a hydrogen ion
• Self-ionization of water
• Acid and base ions co-exist
• Neutral solutions
• H OH-
• Ion product constant (Kw)
• 1.0 x 10-14

6
Classifying Acids/Bases

• Acidic solution
• H gt OH-
• Basic solution (alkaline)
• H lt OH-
• Calculate H or OH- from Kw
• Examples
• If H is 1.0E-4M, classify/determine OH-.
• If OH- is 3.0E-7, classify and determine H.

7
Calculating pH and pOH

• pH scale
• pH - log H
• Use scientific notation for concentrations
• Review logarithms
• Neutral (pH 7.0)
• Acidic (pH lt 7.0)
• Basic (pH gt 7.0)
• pOH -logOH-
• pH pOH 14

8
Examples

• H 1e-6M, 0.0001M find pH of each.
• OH- 1e-2M, 1e-11M find pH of each.
• Calculating H from pH
• pH 6.0, what is H?
• Examples
• pH 4.0, 11.0, calc H
• pH 6.0, 9.0, calc OH-

9
More pH Calculations

• What happens when concentrations are not 1s?
• Calc pH if H 5.0e-6M, and 8.3e-10M
• Calc pH if OH- 2.0e-5M, and 4.5e-11M
• Calc H if pH 5.0, and pH 11.8

10
(No Transcript)
11
Acids and Bases - Theories

• Arrhenius acids and bases
• Acids ionize to yield hydrogen ions (H) in
  solution, Bases ionize to yield hydroxide (OH-)
  in solution
• Monoprotic, diprotic, polyprotic acids
• Too narrow in definition
• Writing Equations
• HCl ? H and Cl-
• Na H2O ? NaOH and H2
• NaOH ? Na and OH-

12
Bronsted-Lowry acids and bases

• Arrhenius does not cover some known acids and
  bases
• Acid hydrogen-ion donor
• HCl H2O ? H3O Cl-
• Base hydrogen-ion acceptor
• Example NH3 H2O forms OH- ion

13
Identifying Conjugate Acids and Bases

• Conjugate acid what is formed when base gains
  hydrogen ion
• Conjugate base what remains when acid donates
  hydrogen ion
• Identify from examples above
• Conjugate acid-base pairs
• Amphoteric H2O, HSO4-

14
Lewis Acids and Bases

• Bronsted-Lowry still did not include some
  substances that behaved as acid/base
• Example NH3 BF3
• Lewis acid substance that accepts a pair of
  electrons in a covalent bond
• Lewis base substance that donates a pair of
  electrons in a bond
• Practice
• PCl3 acid or base?
• AlCl3 Cl- ? AlCl4-

15
Difference between strong and weak acids

• Strong acids completely ionize in solution
• HCl hydrochloric acid
• HNO3 nitric acid
• H2SO4 sulfuric acid
• HBr hydrobromic acid
• HI hydroiodic acid
• HClO4 perchloric acid
• Weak acids partially ionize in solution
• Equilibrium reactions
• Examples any other acid
• acetic acid

16
Strong and Weak Bases

• Strong bases dissociate completely into metal
  ions and hydroxide ions
• LiOH lithium hydroxide
• NaOH sodium hydroxide
• KOH potassium hydroxide
• RbOH rubidium hydroxide
• CsOH cesium hydroxide
• Weak bases equilibrium reaction
• Ex. NH3, H2O

17
Calculate acid dissociation constants

• Equilibrium expressions for weak acids
• Ka acid dissociation constant (same as Keq)
• Recall Keq and product favorability
• low Ka (Keq) favors reactants,
• high Ka favors products
• Order acids and bases by higher or lower Kas and
  Kbs
• Example
• Monoprotic acid has concentration of 0.2M, H
  9.86E-4M at equilibrium. What is the pH and the
  value of Ka for this acid?

18
Lab 36 Disturbing Equilibrium

• Objectives Predict using Le Chateliers
  Principle, confirm with Lab Experiments
• Techniques Predict First!
• Safety KSCN stains
• Questions No Design Experiment

19
Lab 38 Reactions of Acids

• Objectives View basic reactions of acids
• Technique Caution with 6M HCl
• Questions No Design Experiment

20
Day 12/15

• 45 Discuss HW/Demos
• 60 Neutralization
• 15 Activity Nuts/Bolts?
• 30 Start Redox
• Lunch
• 45 Redox
• 120 Lab Formal Report

21
Acid-Base Indicators

• Indicators
• Acid or base that undergoes dissociation in a
  known pH range
• Acid form / Base form equilibrium
• Examples of indicator solutions
• Bromothymol blue CO2 test
• Methyl orange
• Red cabbage
• pH meters

22
Acid-Base Titrations

• Acid plus Base Salt and Water
• Neutralization reaction
• Double replacement reaction
• Practice
• HNO3 KOH
• HCl Ca(OH)2
• H2SO4 NH3

23
Titrations

• Addition of known amount of solution of known
  concentration to determine the concentration of
  another solution
• Practice moles of base/acid needed to
  neutralize?
• 0.25 moles of HNO3
• 1.86 moles of Ca(OH)2
• Standard solutions
• Use known concentration to determine
  concentration of another solution (unknown)
• End point when indicator changes color
• Practice
• Start with balanced equations first!
• ? 0.50M HCl must be added to 25 mL of 1.00 M KOH
  to make neutral
• What is molarity of H3PO4 if 15.0 mL of solution
  neutralized by 38.5 mL of 0.15 M NaOH?

24
Equivalents

• Some acids and bases have different amount of
  H or OH-
• Equivalent
• Amount of acid that will give one mole of
  hydrogen or hydroxide ions
• 1 H3PO4 3 moles of hydrogen ions
• 1 Ca(OH)2 2 equivalents of base

25
Normality

• Concentration expressed as number of equivalents
  of solute in one liter of solution
• Molarity x Number of Equilivalents
• Equiv V(L) x N
• Equivalence point
• Point of neutralization
• Equivalents of acid and base are equal
• N1 X V1 N2 X V2
• Examples
• ? mL of 3.0 N KOH are needed to prepare 600 mL of
  0.20N KOH

26
Salts in detail

• Salts obtained from acid and base neutralization
  (along with water)
• Combinations
• Strong acid strong base neutral solution
• Strong acid weak base acidic solution
• Weak acid strong base basic solution

27
Buffers

• Solutions in which the pH remains relatively
  constant when small amounts of acid or base are
  added
• Blood as buffer
• Illustrate with equations (acetic acid)
• Acid reacts with additional base ions
• Conjugate base ion reacts with additional acid
• Buffer capacity amount of acid or base that can
  be added to buffer before significant pH change
  occurs
• Example
• H2PO4-/HPO42-

28
Solubility Product Constant

• Keq for solubility equations
• Solids constant concentration, not included in
  equation
• Ksp product of concentration terms raised to
  coefficients
• Examples
• Lead (II) Chromate solubility equilibrium
• Ksp 3.9 E-11
• Lead (II) Iodide
• Ksp 7.9E-9

29
Common Ion Effect

• Common ion ion that is common to both salts
• Will affect equilibrium starting concentrations
• Predicting whether precipitation will occur
• Reaction Quotient (Q)
• Ksp at present use current concentrations of
  reactants and products to determine Q, compare
  to Ksp
• Q gt Ksp- YES
• Qlt Ksp NO
• Examples
• What is concentration of sulfide ion in 1.0 L
  solution of iron(II) sulfide to which 0.04 mol of
  iron(II) nitrate has been added? The Ksp of FeS
  is 8 E-19.
• Would precipitation occur when 500 mL of 0.02M of
  AgNO3 is mixed with 500 mL of 0.001M NaCl? Ksp
  of AgCl is1.8 E-10.