Slide 22: picture of Arrhenius and reception to work added

Slide 25: space added between ref and 1 and 2

Slide 32: fixed subscript

Slide 40: added strong and weak acid labels

Intersection 10: Acids and Bases

11/7/06Reading: 16.1 (p765-770) 16.3-16.7

(p773-794)

Outline

• Equilibrium wrap up• Acids and Bases

– History– Models– Modern production– Dissociation

Equilibrium

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

Where does the “equal” in equilibrium come from?

products and reactants

dynamic

completion

concentrations

rates

Keq

Equilibrium is Everywhere• Iodine thermometer

Pictures from: jchemed.chem.wisc.edu/.../ 2003/Aug/abs878_1.html

Equilibrium is Everywhere

Salting the roads

Is ice in equilibrium?

Picture from: www.glrc.org/story. php3?story_id=1377

http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-salt-melts-ice.shtml

What happens when salt is added to snowy winter roads?

Question 1

Apatite, Ca5(PO4)3OH is the mineral in teeth.Ca5(PO4)3OH(s)  5 Ca+2(aq)  + 3PO4

-4(aq)  +  OH-(aq)

On a chemical basis explain why drinking milk strengthens young children's teeth.

Muddiest Point from last week

Q ????If you have the following equilibriumH2 + I2 2 HI Keq = 25

If you have 1 mol H2, 2 mol I2 and 3 mol HI, will you make more H2 or HI?

CrO4-2(aq) + 2H+(aq) ↔ Cr2O7

-2(aq) + H2O(l)

Explain what will happen to the equilibrium if water is added to this system?

Question 2

From: www.funsci.com/fun3_en/ acids/acids.htm

Acids and Bases

What makes something acidic/basic?

What do you know about acids and bases?

Who can name the most?

2000 Top 20 Chemicals Produced in US*

*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/Sulf&top/Sulf&Top.html

Chemical 109 kg 109 kg1. Sulfuric acid 39.62 11. Nitric acid 7.992. Ethylene 25.15 12. Ammonium nitrate 7.493. Lime 20.12 13. urea 6.964. Phosphoric acid

16.16 14. Ethyl benzene 5.91

5. Ammonia 15.03 15. Styrene 5.416. Propylene 14.45 16. Hydrochloric

acid4.34

7. Chlorine 12.01 17. Ethylene oxide 3.878. 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

History of Acids and Alkalies

www.catskillarchive.com/ dwellers/g.htmnefertiti.iwebland.com/ timelines/topics/drink.htm

…a Brief History

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.

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).

…a Brief History

…GlauberMid-1600's Johann Rudolph Glauber

NaCl + H2SO4 HCl + Glauber’s salt

Acid + base = salt + water“Liquor fixus (KOH or K2CO3 solution) and spiritus acidus nitri

(HNO3) are in their nature…totally unlike, foes and adversaries of each other…and when the two are brought together…and 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).”

… All Acids and Alkali Theory

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?

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."

… Bolye

… Lemery

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.  

Acids: Oxygen or Hydrogen?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.  

Dualistic TheoryFollowing 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

Arrhenius Model

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-

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

Acid Base Reactions

HCl + NaOH

HNO3 + KOH

H+ or Hydronium?

H+ proton + H2O H3O+

Hydronium

H3O+ (H2O)6 ref 1

H3O+ (H2O)20 ref 2

H9O4 + ref 3

H5O2+ ref 4

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.

Figures: http://itl.chem.ufl.edu/2045/lectures/lec_x.htmlhttp://cwx.prenhall.com/petrucci/medialib/media_portfolio/17.html

Bronsted-Lowry Model

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.

Bronsted Lowry Practice

HCl + NH3

HNO3 + KOH

HCl + NaOH

Acid: proton donor; Base: proton acceptor; Conjugate acid; conjugate base

Acids and Bases: Comparing Definitions

Arrhenius BronstedAcid provider of H+ in

water Proton donorBase 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

If baseballs were really “base”balls….

+

Measurement of Acids and Bases

pH = -log[H3O+]

HCl + H2O →  H3O+ + Cl-

A 1.0 M solution of HCl would produce 1.0 M H3O+

pH = -log [H3O+]

     = -log[ 1.0M]     = 0

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-]?

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?

pOHpOH = - log[OH-] 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 =       [H3O+]*[OH-] = 1 x10-14

        -log ([H3O+]*[OH-]) = - log (1 x10-14) -log [H3O+] - log[OH-] = 14                     pH + pOH = 14

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

Can you explain the following?

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

Another Equilibrium Constant Ka

For the reaction HA(aq) +  H2O(l)  →  A- (aq)  +   H3O+

(aq)    

Ka = ([H3O+][A-]) / [HA]

Find the Ka for 0.1 M HNO2 using the pH = 2.2

Vocabulary

Strong (16 definitions):

Weak (10 definitions):

Favorable reaction..

ionizing freely in solution

ionizing only slightly in solution

Strong Reaction

exothermicspontaneous

product favored

goes to completion

Strong Acids BasesAn 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                                           conj. 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                                          conj baseKa = ([H3O+][ClO2

-]) / [HClO2]

Strong BasesA 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                                             conj. 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)3NH+][OH-]) / [(CH3)3N]

Strong Acid

Weak Acid

There are six strongly dissociating acids:HClHBrHIHNO3

HClO4

H2SO4 There are also five bases that dissociate completely in solution (strong):LiOHNaOHKOHCa(OH)2

Ba(OH)2

 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.

PracticeTrimethylamine (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?

What kinds of hydrogen atoms (protons) are acidic?

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

O

C

HO

C

CC

O

OH

OH

H

H

OH

Organic Acids

CR

O

OH

+ H2O

CR

O

O-

+ H3O+

RCOOH

CR

O-

O

Bases

OHR3N

H2N CH C

CH3

OH

OH2N CH C

CH2

OH

O

CH2

C

OH

O

HN

C OH

O

Collecting Samples

Obtain Whirl pack bagsHow 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!

Blanks

• Field blank– Controls for contamination during travel

• Lab Blank– Controls for contamination during analysis