Intersection 10: Acids and Bases

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Intersection 10 Acids and Bases

• 11/7/06
• Reading 16.1 (p765-770) 16.3-16.7 (p773-794)

2
Exam 1, Problem 12 Regrade
Please turn in your exams by noon on Tuesday,
11/14
3
Outline
A

• Equilibrium wrap up
• From last week
• Two everyday examples
• Practice questions
• Acids and Bases
• History
• Models
• pH Scale
• Dissociation
• Identifying acids and bases

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Equilibrium
A

• What are the characteristics of an equilibrium
  reaction? Use each of the following words in a
  sentence that describes an equilibrium reaction

products and reactants
concentrations
dynamic
rates
completion
Keq
Where does the equal in equilibrium come from?
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Can Equilibrium be Changed?
A
Use LeChâtelier's Principle to predict what you
will see
Fe(NO3)3 KSCN ? Fe(SCN)2 KNO3 DH
lt 0
red
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Q trumps LeChâtelier
M

• CaCO3(s) ? CaO(s) CO2(g)     ?H gt 0
• Using each method, explain what will happen to
  the concentration of CO2 if solid lime (CaO) is
  added to the system?

7
Equilibrium is Everywhere
M

• Iodine thermometer

Pictures from jchemed.chem.wisc.edu/.../
2003/Aug/abs878_1.html
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Equilibrium is Everywhere
A

• Salting the roads
• Is ice in equilibrium?

http//antoine.frostburg.edu/chem/senese/101/solut
ions/faq/why-salt-melts-ice.shtml
Picture from www.glrc.org/story.
php3?story_id1377
What happens when salt is added to snowy winter
roads?
9
Question 1
A

• Apatite, Ca5(PO4)3OH is the mineral in teeth.
• Ca5(PO4)3OH(s)  5 Ca2(aq)   3PO4-4(aq)
     OH-(aq)
• On a chemical basis explain why drinking milk
  strengthens young children's teeth.

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Problem 1
M

• Given the following equilibrium
• H2 I2 ?? 2 HI Keq 25
• If you have 1 mol H2, 2 mol I2 and 3 mol HI in a
  1 L flask, will you make more H2 or HI?

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Question 2
M

• CrO4-2(aq) 2H(aq) ? Cr2O7-2(aq) H2O(l)
• Explain what will happen to the equilibrium if
  water is added to this system?

12
From www.funsci.com/fun3_en/ acids/acids.htm
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Acids and Bases
A
What do you know about acids and bases?

• What makes something acidic/basic?

Who can name the most?
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2000 Top 20 Chemicals Produced in US
A
Chemical 109 kg 109 kg
1. Sulfuric acid 39.62 11. Nitric acid 7.99
2. Ethylene 25.15 12. Ammonium nitrate 7.49
3. Lime 20.12 13. urea 6.96
4. Phosphoric acid 16.16 14. Ethyl benzene 5.91
5. Ammonia 15.03 15. Styrene 5.41
6. Propylene 14.45 Hydrochloric acid 4.34
7. Chlorine 12.01 17. Ethylene oxide 3.87
8. Sodium hydroxide 10.99 18. Cueme 3.74
9. Sodium carbonate 10.21 19. Ammonium sulfate 2.60
10. Ethylene chloride 9.92 20. 1,3-butatdiene 2.01
It does not include minerals which do not
require processing, such as salt and sulfur, and
petrochemical feedstocks, such as ethane and
butane, which are considered products of oil
companies.
http//scifun.chem.wisc.edu/chemweek/Sulftop/Sulf
Top.html
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History of Acids and Alkalies
A

• www.catskillarchive.com/ dwellers/g.htm

nefertiti.iwebland.com/ timelines/topics/drink.htm
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a Brief History
A

• The only acid know to the ancient Egyptians,
  Greeks, and Romans was______? It was made by air
  oxidation of fermented fruit juice (wine)
• Among the alkalies known to the ancients were
  potash (potassium carbonate) obtained from____,
  soda (sodium carbonate) made by evaporation of
  alkaline waters, and lime (calcium oxide) made by
  roasting________. Caustic potash and caustic soda
  (potassium and sodium hydroxides) were made by
  the action of lime on soda and potash.

Kauffman, G. B. "The Bronsted-Lowry Acid-Base
Concept" J. Chem Ed. 1988, 65, 2831.
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a Brief History
A

• Later, during the middle ages, the alchemists
  learned to make aqua frotis (nitric acid), aqua
  regia (a nitric-hydrochloric acid mixture), and
  oil of vitriol (sulfuric acid).

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Glauber
A

• Mid-1600's Johann Rudolph Glauber
• 2 NaCl H2SO4 ? 2 HCl Glaubers salt
  (Na2SO4)
• Acid base salt water
• KOH HNO3 ? KNO3 H2O
• Liquor fixus (KOH or K2CO3 solution) and
  spiritus acidus nitri (HNO3) are in their
  naturetotally unlike, foes and adversaries of
  each otherand when the two are brought
  togetherand the one part has overcome and killed
  the other, neither a fiery liquor nor a spiritus
  acidus can be found in their dead bodies, but the
  same has been made, as both were before and from
  which they were derived namely ordinary saltpeter
  (KNO3).

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All Acids and Alkali Theory
M

• Otto Tachenius and Francois Sylvius tried to
  simplify the chemistry of life processes by
  reducing all chemical interactions within the
  living organism to acid-base reactions.   
•  
• What evidence can you think of to support or
  discredit the theory of Tachenius and Sylvius?

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Boyle
M

• Boyle (1663) noted that acids, in addition to
  their sour taste, had exceptional solvent power,
  the ability to color certain blue vegetable dyes
  red, and a precipitating action on dissolved
  sulfur.  
• Alkalies, on the other hand, had a slippery feel
  and detergent properties, the ability to dissolve
  oils and sulfur, and the capacity to counteract
  acids and destroy their properties.  Boyle's
  tests showed that some substances were neutral
  and did not classify either as acids or
  alkalies."

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Lemery
M

• Nicholas Lemery (1675) described acids as having
  sharp spiky atoms, which produced a pricking
  sensation on the skin, and alkalies as being made
  up of round particles, which made them feel
  slippery or soapy.  
•  
• When acids and bases were mixed, he pictured the
  sharp needles of the acids as penetrating the
  porous alkali globules, thus producing salts,
  which were neither stinging nor slippery to the
  touch.  

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Acids Oxygen or Hydrogen?
M

• Antoine Lavoisier named the gaseous element
  oxygen in 1777.  When sulfur or phosphorus was
  burned in oxygen, the products dissolved in water
  to form acids, so he concluded that oxygen was
  the element common to all acid materials.   
• Claude Louis Berthollet (1789) showed that
  prussic acid (HCN) did not contain oxygen
• Humphry Davy proved Lavoisier's error more
  convincingly with muriatic acid (HCl), a very
  strong acid.  

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Dualistic Theory
M

• Following the development of the battery by
  Alessandro Volta (1800), chemists began to use
  this new device to decompose all kinds of
  substances.   Jons Jacob Berzelius and William
  Hisinger (1803) found that when salt solutions
  were subjected to electrolysis, bases were found
  at the negative pole and acids at the positive
  pole.  They interpreted this to mean that acids
  and bases must carry opposite electrical charges.
•  
• Berzelius concluded that acid-base reactions were
  simply the result of electrical attractions. His
  dualistic theory (1812) explained all chemical
  interactions in terms of neutralization of
  opposite electrical charges

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Arrhenius Model
M
(PhD describing this work received lowest
possible rating from his University)

• Svante August Arrhenius, during his study of
  electro-chemistry, observed that solutions of
  salts, acids, and bases were the only liquids
  that would conduct an electric current.  He
  suggested (1884) that when these compounds
  dissolved in water they dissociated into charged
  particles, which he called "ions."   
• According to the Arrhenius theory acids are
  compounds that produce hydrogen ions in water
  solution  HCl ?H Cl- and bases are substances
  that provide hydroxide ions in water solution
   NaOH ? Na OH-

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H ions in waterHydronium?
A

• HCl(aq) H (aq) (proton) Cl-(aq)

H2O
H3O (aq) (hydronium)
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Hydronium
A

• H3O (H2O)6 ref 1
• H3O (H2O)20 ref 2
• H9O4 ref 3
• H5O2 ref 4

Figures http//itl.chem.ufl.edu/2045/lectures/le
c_x.html http//cwx.prenhall.com/petrucci/medialib
/media_portfolio/17.html

1. Zavitsas, A.A. (2001) Properties of water
   solutions of electrolyes and nonelectrolytes J.
   Phys. Chem. B 105 7805-7815.
2. Hulthe, G. Stenhagen, G. Wennstrom, O.
   Ottosson, C.H. (1997) Water cluster studied by
   electrospray mass spectroscopy. J. Chromatogr. A
   512 155-165.
3. Zundel, G. Metzger, H. (1968) Energiebander der
   tunnelnden Ubershub-Protenon in flussigen Sauren.
   Eine IR-spektrokpische Untersuchung der Natur
   der Gruppierungen H5O2 Z. Phys. Chem. 58
   225-245.
4. Wicke, E. Eigen, M. Ackermann, Th. (1954) Uber
   den Zustand des Protons (Hydroniumions) in
   waBriger Losung Z. Phys. Chem. 1 340-364.

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Acid Base Reactions
A

• HCl (aq) NaOH (aq) ?
• HNO3 (aq) KOH (aq) ?

H2O (l) NaCl (aq)
H2O (l) KNO3 (aq)
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Bronsted-Lowry Model
A

• Edward Franklin (1905)
• NH4Cl NaNH2 ? NaCl 2 NH3
• Thomas Martin Lowry in England and Johannes
  Nicholas Bronsted in Denmark (1923) independently
  arrived at a more inclusive definition of the
  neutralization reaction as the transfer of a
  hydrogen ion (a proton) from an acid to a base.

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Bronsted Lowry Practice
A
HCl (aq) NaOH (aq) ? HNO3 (aq) KOH (aq) ?
H2O (l) NaCl (aq)
H2O (l) KNO3 (aq)

• HCl NH3?

NH4Cl
Acid proton donor Base proton acceptor
Conjugate acid conjugate base
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Acids and Bases Comparing Definitions
A
Arrhenius Bronsted
Acid provider of H in water proton donor
Base provider of OH- in water proton acceptor
Neutralization formation of water proton transfer
Equation H OH- ? H2O HA B ? BH A
Limitations water only proton transfer
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If baseballs were really baseballs.
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Measurement of Acids and Bases
M

• pH -logH3O
• HCl H2O ?  H3O Cl-
• A 1.0 M solution of HCl would produce 1.0 M H3O
• pH -log H3O
•       -log 1.0M
•       0

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M
pH H3O pH H3O
0 1 M 8 1x10-8
1 0.1 9 1x10-9
2 0.01 10 1x10-10
3 0.001 11 1x10-11
4 1x10-4 12 1x10-12
5 1x10-5 13 1x10-13
6 1x10-6 14 1x10-14
7 1x10-7
How do you measure base OH-?
34
M

• Water undergoes an equilibrium process called
  autoionization.2 H2O(l) ? H3O(aq)    OH-(aq)
• Write out the expression for the equilibrium
  constant (Kw) of this reaction.
• In water, the H3O and OH- ions are always in
  equilibrium with water having an equilibrium
  constant (Kw) of 1x10-14
• In pure water H3O OH- 1x10-7 M.  What
  about the pH?

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pOH
M

• pOH - logOH-
• Remember that a low pH corresponds to a high
  concentration of H3O (acidic) solution.
  Therefore, a low pOH corresponds to a high
  concentration of OH- (basic) solution.
• Kw        H3OOH- 1 x10-14
•         -log (H3OOH-) - log (1 x10-14)
•  -log H3O - logOH- 14
•                      pH pOH 14

36
M
pH H3O pOH OH-
battery acid, concentrated HF 0 1 M 14 1x10-14
HCl secreted by stomach lining 1 0.1 13 1x10-13
lemon juice, gastric acid, vinegar 2 0.01 12 1x10-12
grapefruit, orange juice, soda 3 0.001 11 1x10-11
tomato juice, acid rain 4 1x10-4 10 1x10-10
soft drinking water, black coffee 5 1x10-5 9 1x10-9
urine, saliva 6 1x10-6 8 1x10-8
"pure water" 7 1x10-7 7 1x10-7
sea water 8 1x10-8 6 1x10-6
baking soda 9 1x10-9 5 1x10-5
Great Salt Lake, milk of magnesia 10 1x10-10 4 1x10-4
ammonia solution 11 1x10-11 3 1x10-3
soapy water 12 1x10-12 2 1x10-2
bleaches, oven cleaner 13 1x10-13 1 1x10-1
liquid drain cleaner 14 1x10-14 0 1
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Question 3 Can you explain the following?
A
Acid pH H3O
0.1 M HCl 1.0 0.1 M
0.1 M acetic acid CH3COOH 2.9 1.26x10-3
0.1 M nitric acid HNO3 1.0 0.1 M
0.1 M nitrous acid HNO2 2.2 6.3 x10-3
0.1 M hypochlorous acid HOCl 4.2 6.3 x10-5
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Problem 2
A

• HA(aq)  H2O(l)  ?  A- (aq)     H3O(aq)    
• What is the expression for the equilibrium
  constant?

Ka (H3OA-) HA
Find the Ka if a 0.1 M HNO2 measures a pH 2.2
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Vocabulary
A

• Strong (16 definitions)
• Weak (10 definitions)
• Favorable reaction..

ionizing freely in solution
ionizing only slightly in solution
Strong Reaction
goes to completion
spontaneous
exothermic
product favored
40
Strong Acids Bases
A

• An acid that dissociates completely (the
  equilibrium is shifted all of the way to its
  conjugate base and hydronium ion) is said to be a
  strong acid.
• HCl(aq)  H2O(l) ?   H3O(aq) Cl-(aq)
• acid                                           con
  j. base
• An acid that does not dissociate completely (an
  equilibrium is established in solution between
  the acid, its conjugate base, and hydronium ion)
  is said to be a weak acid.
• HClO2(aq) H2O(l)  ?  H3O(aq) ClO2- (aq)     
• acid                                          co
  nj base
• Ka (H3OClO2-) / HClO2

41
Strong Bases
A

• A base that dissociates completely (the
  equilibrium is shifted all of the way to its
  conjugate acid and hydroxide) is said to be a
  strong base.
• NaOH(aq)   H2O(l) ?   OH-(aq) Na(aq)
• base                                             c
  onj. acid
• A base that does not dissociate completely (an
  equilibrium is established in solution between
  the base, its conjugate acid, and hydroxide) is
  said to be a weak base.
• (CH3)3N(aq)    H2O(l)   ? (CH3)3NH(aq)   OH-(aq
  )   
• base                            conj. acid
  
• Kb ((CH3)3NHOH-) / (CH3)3N

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A
43
A

• There are six strongly dissociating acids
• HCl HNO3
• HBr HClO4
• HI H2SO4 
• There are also five bases that dissociate
  completely in solution (strong)
• LiOH Ca(OH)2
• NaOH Ba(OH)2
• KOH
•  
• You should commit the strong acids and bases to
  memory.
• Appendix F in your text book lists Ka and Kb
  values for many weakly dissociating acids and
  bases.

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Problem 3
M

• Trimethylamine (CH3)3N has a Kb of 6.5 x10-5.  
• Write out its chemical reaction with water
•  
• What is the OH- of a 0.010 M solution of
  triethylamine?
•  
• What is the pOH?
•  
•  
• What is the pH?

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What kinds of hydrogen atoms (protons) are acidic?
M

• H-halogen (HF, HCl, HBr, HI)
• H2O
• H2S (Ka1 8.9x10-8)
• Oxoacids (H-polyatomic ions) (H2CO3, HNO3, etc.)
• HCN

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Organic Acids
M
RCOOH
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Bases
M

• OH
• R3N

48
(No Transcript)
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Collecting Samples
M

• Obtain Whirl pack bags
• How do you fill the bags?
• How many samples should you take?
• How to store samples?
• Filter (acid wash all glassware)
• You may need special sampling techniques!

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Blanks
M

• Field blank
• Controls for contamination during travel
• Lab Blank
• Controls for contamination during analysis