“A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry.
Download ReportTranscript “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry.
“A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Chemistry General FITCH Rules G1: Suzuki is Success G2. Slow me down G3. Scientific Knowledge is Referential G4. Watch out for Red Herrings G5. Chemists are Lazy C1. It’s all about charge C2. Everybody wants to “be like Mike” qq qq C3. Size Matters or k E k d r r C4. Still Waters Run Deep C5. Alpha Dogs eat first 1 2 el 1 2 1 2 Properties and Measurements Property Size Volume Weight Temperature Unit m cm3 gram Reference State size of earth m mass of 1 cm3 water at specified Temp (and Pressure) oC, K boiling, freezing of water (specified Pressure) amu (mass of 1C-12 atom)/12 atomic mass of an element in grams atm, mm Hg earth’s atmosphere at sea level 1.66053873x10-24g quantity mole Pressure Energy, General electronic states in atom Electronegativity Heat flow measurements Standard Molar Enthalpy Energy of electron in vacuum F constant pressure, define system vs surroundings per mole basis (intensive) 25 oC, 1 atm, from stable state Hfo Haq+ =0 We ended our last module considering the two following reactions: 2 Pbs O2( g ) 2 PbO G 355kJ kJ 355 mol Ke G 0 RT e kH 8.314 x 10 3 298 K mol K K e143 127 x1062 We also had looked up K for the reaction of Fe rusting K for rusting of Fe = 10261 Will these reactions proceed the same way in solution as in air oxidation? Could we “capture” the energy of these reactions more efficiently than a fire? Do “bugs” make fires to get their energy?, If not can we mimic them? “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Some review of relevant Energy concepts Thermochemistry and work Free energy and maximum work Chemical reactions involve Zn(s) 2 H (aq) Zn 2 (aq) H2 ( g) 1. heat exchange As a review: Heat exchange Constant At constant Atm.pressure Pressure who is oxidized? who is reduced? what is the oxidation number on H2? Who is an oxidizing agent? thalpein – to heat en - in H for (?) heat H = Greek: enthalpy qP H Subscript Reminds us that Pressure is constant 1 atm pressure = constant pressure This means heat flow, q, is enthalpy change Chemical reactions involve Zn(s) 2 H (aq) Zn 2 (aq) H2 ( g) 1. heat exchange constant Atm. pressure 2. work V PressureVolume work w P V I feel a Noble Prize coming on Maximize work!!! Solve Global Warming five Navy Avengers disappeared in the Bermuda Triangle on Dec. 5, 194 One possible source of energy =????? 3 to 8 standard cubic feet of biogas per pound of manure. The biogas usually contains 60 to 70% methane. Methane Gas Recovery At landfills How much PV work occurs for 1 atm constant T burning of methane as a free volume fire? CH4( g ) 2O2( g ) CO2( g ) 2 H2 O( l ) PV nRT Work is done by the system on the reaction (compression) At constant T, 1 atm P: P V n RT P V n gas final n gas initial RT L atm P V 1 3moles 0.0821 298K mol K P V 48.9316 L atm %&$*! Conversions . kJ 01013 P V 48.9316 L atm 4.9kJ L atm 2mole change Consider the contribution of volume change for water in this reaction CH4( g ) 2O2( g ) CO2( g ) 2 H2 O( l ) 2moleH O 2 (l ) 3 18 g 1 cm water 1L * * * 3 3 0.036 L mol 1gwater 10 cm %&$*! Conversions 01013 . kJ PV 1atm 0.036 L 0.0036kJ L atm Most reactions total (q): PV 1 mole gas PV 2mole liquid water Energy in kJ ~ 1000 kJ ~ 2.5 kJ ~ 0.0036 kJ Sig fig tells us that PV energy small compared to q H 890kJ CH4( g ) 2O2( g ) CO2( g ) 2 H2 O(l ) w PV 4.9kJ 0.0036kJ 4.90036kJ Enclosing the reaction In a combustion engine Allows us to capture work Total INTERNAL energy Enthalpy Of an isolated system Or heat exchange work Constant P There is a sign change which Indicates we get to use the work ΔE Bunsen burner (open) -885kJ Automobile engine (closed) -885kJ Fuel Cell, theoretical no heat transfer -885 kJ ΔH -890kJ -665kJ -67kJ Maximum non expansion work at constant pressure and temperature is G wnon,exp ansion,max,cons tan tT , P w +5kJ -220kJ -818kJ Grx Hrx T Srx If T or Srx 0 Then Grx Hrx If T 0 or Srx 0 Then Grx Hrx K does not go below 0 So this is impossible H 890kJ Maximum work less Than total internal energy CH4( g ) 2O2( g ) CO2( g ) 2 H2 O(l ) More organized phases Maximum work less than internal energy because energy used to create a more organized phase “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Some review of relevant Energy concepts Units of energy and work energy force dis tan ce work Power time time d 212 ft 12 ft Wikepedia 32,572 ft lbforce 2.4 1hp 180lbs 212 ft min utes min 32,572 ft lbforce min 542.8667 fl lbf 60s min s Nm J 542.8667 ft lbforce 0.3048m 4.44822 N 745.699 745.699 s lbf s s 1 ft J 1hp 745.699 s average horse peak average horse average hp 14.9 R.D. Stevenson and R. J. Wasserzug <1 hp Nature, 364, 195-195, Jul 1993 Properties and Measurements Property Size Volume Weight Unit m cm3 gram Temperature 1.66053873x10-24g quantity mole Pressure Reference State size of earth m mass of 1 cm3 water at specified Temp (and Pressure) oC, K boiling, freezing of water (specified Pressure) amu (mass of 1C-12 atom)/12 atomic mass of an element in grams atm, mm Hg earth’s atmosphere at sea level kg m 2 F ma kg P s2 A A ms m Energy, General Animal hp BTU Heat Gram Calorie horse on tread mill, 745 J/s lb water oF g water oC British Thermal Unit (>1700 AD) Energy required to raise one lb of water at it’s maximum density (39.1 oF) 1 oF Energy to raise 1 g of water by 1 oC Means “defined as” Kinetic energy kg m2 1 1J oule 2 s 1 2 E k mv 2 2 kg mass moving at 1 m/s 1 1m E k 2kg s 2 kg m Ek 1 s2 2 2 James Joule (1818-1889) English Physicist who related Heat energy to animal work (to sell steam engines) Properties and Measurements Property Size Volume Weight Unit m cm3 gram Temperature 1.66053873x10-24g quantity mole Pressure Reference State size of earth m mass of 1 cm3 water at specified Temp (and Pressure) oC, K boiling, freezing of water (specified Pressure) amu (mass of 1C-12 atom)/12 atomic mass of an element in grams atm, mm Hg earth’s atmosphere at sea level kg m 2 F ma kg P s2 A A ms m Energy, General Animal hp horse on tread mill, 745 J/s heat BTU 1 lb water 1 oF calorie 1 g water 1 oC Kinetic J 2 kg mass moving at 1 m/s Electrostatic 1 electric charge of 1 coulomb in a 1 V field Chemistry Rule #1 = it’s all about Charge nFV J J =Work required to move one electric charge of one coulomb through an Electric potential difference of 1 V J VC kQ1 E el Q2 d Na+ Cl- d Electric potential, V, Exerted by Q1 over distance d on the charge Q2 of object 2 8.99 x10 J m Charge,q And size, D matter! 9 k C oulomb 2 J V C Same old, same old, new names a coulomb is a unit of charge F=Faraday = 96,485 coulombs of charge/mole of e coulombs Joules nmolese molee Coulomb Joules nFV J nFV G neg sign accounts for negative electron V directly relates to free energy Galen, 170 Marie the Jewess, 300 Charles Augustin James Watt Coulomb 1735-1806 1736-1819 Justus von Thomas Graham Liebig (1803-1873 1805-1869 Ludwig Boltzman 1844-1906 Gilbert N Lewis 1875-1946 Henri Louis LeChatlier 1850-1936 Johannes Bronsted 1879-1947 Jabir ibn Hawan, 721-815 Luigi Galvani 1737-1798 Richard AC E Erlenmeyer 1825-1909 An alchemist Count Alessandro G A A Volta, 1747-1827 James Joule (1818-1889) Henri Bequerel 1852-1908 Lawrence Henderson 1878-1942 Galileo Galili Evangelista Torricelli 1564-1642 1608-1647 Amedeo Avogadro 1756-1856 Rudolph Clausius 1822-1888 Jacobus van’t Hoff 1852-1911 Niels Bohr 1885-1962 John Dalton 1766-1844 William Thompson Lord Kelvin, 1824-1907 Johannes Rydberg 1854-1919 William Henry 1775-1836 Johann Balmer 1825-1898 J. J. Thomson 1856-1940 Erwin Schodinger Louis de Broglie 1887-1961 (1892-1987) Fitch Rule G3: Science is Referential Jean Picard 1620-1682 Jacques Charles 1778-1850 Francois-Marie Raoult 1830-1901 Heinrich R. Hertz, 1857-1894 Friedrich H. Hund 1896-1997 Daniel Fahrenheit 1686-1737 Max Planck 1858-1947 Rolf Sievert, 1896-1966 Blaise Pascal 1623-1662 Georg Simon Ohm 1789-1854 James Maxwell 1831-1879 Robert Boyle, 1627-1691 Isaac Newton 1643-1727 Michael Faraday 1791-1867 B. P. Emile Clapeyron 1799-1864 Dmitri Mendeleev 1834-1907 Svante Arrehenius Walther Nernst 1859-1927 1864-1941 Fritz London 1900-1954 Wolfgang Pauli 1900-1958 Johannes D. Van der Waals 1837-1923 Marie Curie 1867-1934 Anders Celsius 1701-1744 Germain Henri Hess 1802-1850 J. Willard Gibbs 1839-1903 Fritz Haber 1868-1934 Thomas M Lowry 1874-1936 Werner Karl Linus Pauling Louis Harold Gray 1905-1965 Heisenberg 1901-1994 1901-1976 “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Some example problems Relating V, free energy, And K For standard conditions (1 mole, 1 atm, 25C): nFV G o o Language Komodo (Indonesia) K o o Greek G nFV G RT ln K The Rosetta Stone Vamale (Polynesia) Vo Different languages, same information. Represent Total free energy (maximum work) associated with a reaction Relationship G, K, V Example Problem 1 : What are K and the standard voltage associated with the oxidation of lead given tabulated standard free energies of formation? (1 atm, 298 K) G o rx n G 0 f , products n G o f ,reac tan ts 2 Pbs O2( g) 2 PbOs 0kJ 0kJ 187.9 kJ 1molO2 G 2molPbOs 2molPbs molPbO molPbs molO2 o rx Grxo 357.8kJ G RT ln K o Ke G 0 RT kJ 357 .8 mol Ke Ke kJ 8.314 x10 3 273 K mol K 158 K 2.89 x1068 Relationship G, K, V Example Problem 1 : What are K and the standard voltage associated with the oxidation of lead given tabulated standard free energies of formation? (1 atm, 298 K) 2 Pbs O2( g) 2 PbOs Grxo 357.8kJ -nFV0 = Go ? K 2.89 x1068 Compound neutral O usually -2 +4 Ox # = 0 So Pb = +2 2(+2)=4 =-4electrons Relationship G, K, V Example Problem 1 : What are K and the standard voltage associated with the oxidation of lead given tabulated standard free energies of formation? (1 atm, 298 K) 2 Pbs O2( g) 2 PbOs G 357.8kJ o rx K 2.89 x1068 -nFV0 = Go ? n=4 nFV o G o 357.8 357.8kJ 1000 J 357 .8kJ 1000 J oo mol rx as written kJ G 1 V o 0.92V V ooo G mol rx as written kJ V nF 4mol electrons 96487coulombs J nF coulomb mol reaction mol electron 2 Pbs O2( g) 2 PbOs G 357.8kJ o rx K 2.89 x1068 V 0.92V o All tell us that reaction Will spontaneously Proceed to the right Favoring products So….V>0 is spontaneous How will we conveniently store info? What will be the reference point? T = boiling water E of electrons – vacuum, far away from the nucleus etc. “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry ½ reactions, standard voltages and Electrochemical “cells” 1. Create a body of reference reactions 2. with a SCALE defined to one reference rx 3. Make an instrument to calibrate or measure the scale. +4e 2 Pbs O2( g) 2 PbOs -4e s 2 Pb 2 2 Pb 4e Simplify for the tables s Pb 2 Pb 2e Could imagine oxygen reacting Similarly with Fe, CH4! Divide reaction into 2 parts O2 g 4e 2O 2 Set a common “grammar” – all comparisons are for reductions 2 Pb 2e Pbs Standard conditions 1 atm, 298 K, 1 M or 1 atm Vo values for 1/2 reactions Compared to protons Reaction Cs+ + e K+ + e Na+ + e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Br2 + 2e Cl2 + 2e F2 + 2e Cs K Na Fe Pb H2(gas) Cu 4OHH2O2 2Br2Cl2F- Vo ? -2.95 -2.71 -0.44 -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 “Medicine is the Art of Observation” (ABB, III, M.D.) 1. 2. 3. 4. 5. 6. 7. 8. 9. What seems to be the “grammar” for the reactions? What is the zero point? What do you expect the value for Cs to be? How do the values for the halogens compare to the group I elements? Is there a trend in the halogens? How does this relate to the periodic chart? How does this relate to “charge density”? Who wants the electrons? Where are the guys that want the electrons located on the chart? don’t have e Reaction Cs+ + e K+ + e Na+ + e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Br2 + 2e Cl2 + 2e F2 + 2e want most have e want least Cs K Na Fe Pb H2(gas) Cu 4OHH2O2 2Br2Cl2F- Vo ? -2.95 -2.71 -0.44 -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 Vo < -2.95 (e.g. -3, -4…) Obeys Rule #2 Everybody Wants to Be Like Mike (get to Group 18 e configuration) 1. Create a body of reference reactions 2. with a SCALE defined to one reference rx 3. Make an instrument to calibrate or measure the scale. Measure flow of e 1atmH2,g Unknown But wait, isn’t there a problem? 1M Haq Reference ½ reaction 2 Haq ,1 M 2e H2 ,1atm Do you think this reaction will continue for long? Here’s a case where spectator ions are importantsolution net nuetrality!!!! 5e MnO4( aq ) 5e 8H(aq ) Mn(2aq ) 4 H2 O 5Fe(2aq ) 5Fe(3aq ) 5e 10 X- 5Fe2+ Net charge =0 Fe3+ Net charge =10(-1)+5(+3) =+5 1MnO4-, 8H+ - - - - - - - + +- + + + + ++ Net charge =0 8 7 X- e Mn2+ Net charge =+2 +7(-1) = +5 Charge build up stops reaction Will want to let spectator ions flow (but not the reactants!) e (current) Fe3+ 5+ - -5 “jelly” (salt bridge) retards motion of Fe3+/2+ MnO4“jelly” allows motion of spectators which produces Charge balance Weird Grammar Rules: Those Italians! Volta discovered this process 1. 2. 3. Always make electrons flow to right Electrons flow down to the cathode (cat = Greek for down). Electrons flow up into the anode (an = Greek for up) Count Alessandro Volta, Italy ~1800, first battery OIL Oxidation is Loss e (current) anode Oxidation electrons taken Out (up = anode) Rig Reduction is Gain Cl- cathode Reduction electrons accepted In (down = cathode) oxidation reduction An An ox ox jumped jumped over over aa red red cat There 2 kinds of electrochemical (or Voltaic) “cells” 1. Spontaneous (Galvanic) Electrochemical cell (V +; free energy -) 2. Non-spontaneous (re-charging or Electrolytic) (V -; free energy +) Prez Bush II’s 2006 State of the Union The coming of the hydrogen economy (Considered much more likely by scientists: Methane based fuel Cell) Hrxo 150.7kJ Hrxo 0 Grxo 2501 . kJ Grxo 0 CH4( g ) H2 O CO( g ) 3H2 ( g ) 3H2( g) 6Haq Resistive energy losses in the external circuit Hrxo 711kJ Grxo 857.4kJ o Hnet rx 560.9 kJ o Gnet rx 607.3kJ 3 2 O2,g 6Haq 3H2 O CH4 ( g ) 2 O2 2 H2 O( l ) CO( g ) 3 Feed hydrogen gas to fuel cell anode To use methane need to a pre-step conversion to hydrogen over a nickel oxide catalyst. CO+3H2 work Ni 3H2 Ni Ni Advantage: methane exists Disadvantage” CH4(g) Less energy H2O recycle Feed air To fuel cell cathode 3/2O2 H+ H+ 6e 6H+ 6e H+ 3H2O H+ H+ H+ Proton conducting polymer to reduce weight Scientific American, Sept 2006 Issue on Energy2005 – big research Bucks from the public Hydrogen Economy 1. H2 production spigot 1. 2. Coal/gasoline/methane conversion = 110gCO2/km driven current cars 150gCO2/km driven 1. Need to capture CO2 and dump and/or 2. Reduce CO2 1. coal/gasoline/methane capture CO2 and pump to ground 2. solar 3. wind 4. nuclear Autos (= ~ 40% U.S. energy consumption) • Proton-exchange membrane – membranes degrade with use fuel cells last only ~2,000 <1/2 necessary for commercial vehicle • Cost of fuel cells – current cost 1M$, could drop to $125/kw ($30/kw combustion engine) • Storage of H2 on the car compression/super cooled metal hydride 4. Safety of compressed H2 5. Timeline – earliest predicted commercialization 20 years Green and red are hydrogen gas on an organic lattice to serve as fuel source Hydrogen gas http://www.physorg.com/news11458.html “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Using Standard Voltages to predict Spontaneous reactions Start arrow on right hand side and end on left hand Reaction Cs+ + e K+ + e Na+ + e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Br2 + 2e Cl2 + 2e F2 + 2e Don’t have want most Have e want least Cs K Na Fe Pb H2(gas) Cu 4OHH2O2 2Br2Cl2F- Vo ? -2.95 -2.71 -0.44 -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 electrons flow down hill away from negative voltage Think of A water tower Start arrow on right hand side and end on left hand Uphill reactions: not probable Reaction Cs+ + e K+ + e Na+ + e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Br2 + 2e Cl2 + 2e F2 + 2e Cs K Na Fe Pb H2(gas) Cu 4OHH2O2 2Br2Cl2F- Vo ? -2.95 -2.71 -0.44 -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 Start arrow on right hand side and end on left hand Can I react F2 with K+? Reaction Cs+ + e Cs K+ + e K Na+ + e Na No, there Fe2+ + 2e Fe is nobody electrons, Pb2+ + 2e Pb 2H+ + 2e H2(gas) source! no electron Cu2+ + 2e Cu O2 + 2H2O + 4e 4OHO2 + 2H+ + 2e H2O2 Br2 + 2e 2BrCl2 + 2e 2ClF2 + 2e 2F- to Vo ? -2.95 -2.71 give -0.44 away -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 Start arrow on right hand side and end on left hand Can I exchange e between Cs with Pb? Reaction Cs+ + e K+ + e Na+ + e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Br2 + 2e Cl2 + 2e F2 + 2e Cs K Na Fe Pb H2(gas) Cu 4OHH2O2 2Br2Cl2F- Vo ? -2.95 -2.71 -0.44 -0.13 0 0.34 0.40 0.68 1.09 1.36 2.87 There is nobody to accept electrons! Example problem Standard V (good exam prototypes) Which reactions will go? a) b) c) d) Cs metal plus KBr? F2 gas plus PbCl2 Na metal plus chlorine gas Na+ + Cl- Strategy: 1. Pick one who has electrons 2. Pick one who doesn’t 3. Draw an arrow, starting where the electron is. 4. Is it up or downhill? Reaction K+ + e Na+ + e NCl3_4H+ + 6e Fe2+ + 2e Pb2+ + 2e 2H+ + 2e N2(g) + 8H+ + 6e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Ag+ + e NO3- + 4H+ + 3e Br2 + 2e 2NO3- + 12H+ + 10e Cl2 + 2e Au+ + e F2 + 2e K Na 3Cl- + NH4+ Fe Pb H2(gas) 2NH4+ Cu 4OHH2O2 Ag NO(g) +2H2O 2BrN2(g) +6H2O 2ClAu 2F- Vo -2.95 -2.71 -1.37 -0.44 -0.13 0 0.275 0.34 0.40 0.68 0.799 0.957 1.09 1.246 1.36 1.83 2.87 Consider 6 of the 7 earliest known pure elements: Au, Ag, Cu, Pb, Sn, Fe Who rusts (reacts with O2) more spontaneously? Why is Au considered sacred or valuable in many cultures across history? Why was Pb used for plumbing? Reaction Fe2+ + 2e Pb2+ + 2e 2H+ + 2e Sn4++2e N2(g) + 8H+ + 6e Cu2+ + 2e O2 + 2H2O + 4e O2 + 2H+ + 2e Fe+3 +e Hg22+ +2e Ag+ + e NO3- + 4H+ + 3e Br2 + 2e 2NO3- + 12H+ + 10e Cl2 + 2e Au+ + e F2 + 2e Fe Pb H2(gas) Sn2+ 2NH4+ Cu 4OHH2O2 Fe2+ 2Hg(l) Ag NO(g) +2H2O 2BrN2(g) +6H2O 2ClAu 2F- Medicine is the Art of Observation Vo -0.44 -0.13 0 0.154 0.275 0.34 0.40 0.68 0.769 0.796 0.799 0.957 1.09 1.246 1.36 1.83 2.87 Saturday Friday Thursday Tuesday Wednesday Monday Sunday ~100 B.C (Context Slide 1) Days of weeks related to 7 planets and “7” metals Less spontaneous Not really Known so Assigned as alloy Changes occur at the time that acids were developed (1100-1400AD) (Islamic Chemists) xM solid 2 O2 M 2 Oy , solid y Less likely to lose e G Air oxidation New assignments M solid n M aqueous ne -V Kf n n M aqueous xLaqueous MLx ,aqueous Change in order here ~1300A.D n M solid xLaqueous MLx ,aqueous ne Chemical oxidation in HCl (Context Slide 2) “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Summing various kinds Of reactions together: Calculations Some Rules 1.Voltages sum 2.Reversed reactions =change of sign 3.When summing voltages only don’t worry about #electrons (n) since V = Joule/coulomb of charge 4.To sum a Voltage and a K: a. first convert both to free energy (now worry about # electrons n) b.Sum the free energies c. Convert the summed free energy back to a Voltage (worry about #electrons n here also) Example Calculation: Summing V equations Given that A e A Vao A e B Vao/b What is the voltage for the reaction: 2 A A B A A e A e B 2 A A B V? Vao Vao/b V Vao/b Vao Standard V for REDUCTION ½ reactions Example Summing V equations: If your lab partner attempts to add fluorine gas to a beaker containing potassium metal what should you do? Justify by calculating the reaction voltage and the free energy F2 , g 2e 2F K e K V 2.87 V o 2.95 2 K 2e 2K V o 2.95 o Say your prayers and duck. Notice here multiplying does not affect V Reversal switches sign, tho 2K 2 K 2e F2, g 2e 2 F 2 K F2 2 K 2 F V o 2.95 V 2.87 o V o 582 . G o nFV o 2 F 582 . 29.648x104 582 . 1123kJ Example Summing Voltages and Ks We saw that the relative rank for easy of oxidation of metals changed Around 1300 A.D. when technology from the Islamic world was developed that allowed for the production of strong acids. What is the standard potential for the oxidation of gold in the presence of 1 M HCl given the following information: Auaq e Aus V o 183 . 1 Auaq 2Cl,aqs AuCl2 ,aq K f 2.71x10 11 Is gold easier or harder to oxidize in 1 M HCl? Organize information into one oxidation reaction Aus Auaq e V o 183 . 1 Auaq 2Cl,aqs AuCl2 ,aq K f 2.71x1011 Aus 2Claq AuCl 2,aq e Sign changes ? Example Summing Voltages and Ks What is the standard potential for the oxidation of gold in the presence of 1 M HCl? Is gold easier or harder to oxidize in 1 M HCl? nFV G RT ln K o Aus Auaq e V o 183 . 1 Auaq 2Cl,aqs AuCl 2 ,aq Aus 2Cl aq AuCl 2,aq K f 2.71x1011 e ?. V 115 o net o G o 177 . x10 5 G o 6.52 x104 o Gnet 111 . x105 Easier to Oxidize in o o 5 G nFV 1 96487 183 . 177 . x10 Presence of 298 ln2.71x1011 652 Go RT ln K 83141 . . x104 HCl a. Convert to free energies b. Sum c. Convert to Vnet 5 5 111 . x 10 111 . x 10 Vneto 115 . nF 1 96487 “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Voltage and Concentrations How does concentration fit In? G G RT ln Q o nFV G G nFV 0 o nFV nFV RT ln Q o o nFV RT ln Q nFV nF nF nF RT V V ln Q nF o RT C D V V ln a b nF A B c o d Nernst Equation: RT C D V V ln nF A a B b c d o At 25 oC C D 0.0592 V V log a b n A B c d o When the reaction favors products, it is Spontaneous, or Galvanic Luigi Galvani: “Frog leg Guy” 1780 Galen, 170 Marie the Jewess, 300 Charles Augustin James Watt Coulomb 1735-1806 1736-1819 Justus von Thomas Graham Liebig (1803-1873 1805-1869 Ludwig Boltzman 1844-1906 Gilbert N Lewis 1875-1946 Henri Louis LeChatlier 1850-1936 Johannes Bronsted 1879-1947 Jabir ibn Hawan, 721-815 Luigi Galvani 1737-1798 Richard AC E Erlenmeyer 1825-1909 An alchemist Count Alessandro G A A Volta, 1747-1827 James Joule (1818-1889) Henri Bequerel 1852-1908 Lawrence Henderson 1878-1942 Galileo Galili Evangelista Torricelli 1564-1642 1608-1647 Amedeo Avogadro 1756-1856 Rudolph Clausius 1822-1888 Jacobus van’t Hoff 1852-1911 Niels Bohr 1885-1962 John Dalton 1766-1844 William Thompson Lord Kelvin, 1824-1907 Johannes Rydberg 1854-1919 William Henry 1775-1836 Johann Balmer 1825-1898 J. J. Thomson 1856-1940 Erwin Schodinger Louis de Broglie 1887-1961 (1892-1987) Fitch Rule G3: Science is Referential Jean Picard 1620-1682 Jacques Charles 1778-1850 Francois-Marie Raoult 1830-1901 Heinrich R. Hertz, 1857-1894 Friedrich H. Hund 1896-1997 Daniel Fahrenheit 1686-1737 Max Planck 1858-1947 Rolf Sievert, 1896-1966 Blaise Pascal 1623-1662 Georg Simon Ohm 1789-1854 James Maxwell 1831-1879 Robert Boyle, 1627-1691 Isaac Newton 1643-1727 Michael Faraday 1791-1867 B. P. Emile Clapeyron 1799-1864 Dmitri Mendeleev 1834-1907 Svante Arrehenius Walther Nernst 1859-1927 1864-1941 Fritz London 1900-1954 Wolfgang Pauli 1900-1958 Johannes D. Van der Waals 1837-1923 Marie Curie 1867-1934 Anders Celsius 1701-1744 Germain Henri Hess 1802-1850 J. Willard Gibbs 1839-1903 Fritz Haber 1868-1934 Thomas M Lowry 1874-1936 Werner Karl Linus Pauling Louis Harold Gray 1905-1965 Heisenberg 1901-1994 1901-1976 Example Concentration Cell: Calculate the cell potential for a spontaneous (galvanic) cell based on the reaction where [Mn2+] = 0.50 M, [Al3+] = 1.50 M At 25 oC, 1 atm 2 aq 2 Als 3 Mn 2 Al 3 aq Know C D 0.0592 V V log n A a B b c d o concentrations 25 oC 1 atm 3 Mns Don’t know n Vo Standard conditions Means we can use tables of standard voltages Example Concentration Cell: Calculate the cell potential for a spontaneous (galvanic) cell based on the reaction where [Mn2+] = 0.50 M, [Al3+] = 1.50 M At 25 oC, 1 atm 2 aq 2 Als 3 Mn 2 Al 3 aq Don’t know n =6 Vo Know C D 0.0592 V V log n A a B b c 3 Mns d o concentrations 25 oC 1 atm 3 2 Als 2 Al aq 6e 3 Mn 2 aq 6e 3 Mn s 2 aq 2 Als 3 Mn 2 Al 3 aq 2 aq 3 Mn 6e 2 Al s 6e 3 Mns 3 2 Als 2 Al aq 6e 2 aq 3 Mn 6e 3 Mns 2 Al 3 aq 3 Mns Std V 166 . grammer o V 118 . o V o 166 . V 118 . o +0.48 Calculate the cell potential for a spontaneous (galvanic) cell based on the reaction where [Mn2+] = 0.50 M [Al3+] = 1.50 M, at25 oC, 1 atm Example Conc. Cell: Calculate the cell potential for a spontaneous (galvanic) cell based on the reaction where [Mn2+] = 0.50 M, [Al3+] = 1.50 M at 25 oC. 1atm 2 3 2 Als 3 Mn aq Know c d 0.0592 C D o V V log n A a B b concentrations n=6 Vo=+0.48 2 Alaq 3 Mns Don’t know 3 aq Al 0.0592 V 0.48 log 2 6 Mnaq What happened to Als and Mns? 150 0.0592 . V 0.48 log 3 6 05 . 2 V 048 . 001 . 047 . 2 3 “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Voltage and Biology http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/redox.htm See also:Awesome site Biological “Galvanic” (Spontaneous) Cell: Respiration Note the negative To positive Arrangement of Voltages. Electrons flow away From the Negative sign. Note also very Small voltage steps, 0.01 V is a large driver! CoQ = Coenzyme Q What is the role of the long tail? Ubiquinone, Q 2e, 2H+ Ubiquinol, QH2 Q 2 H 2e H2 Q ~ 0.6999V 0 Open browser to see and rotate molecule http://www.reciprocalnet.org/recipnet/showsample.jsp?sampleId=27344188&sampleHistoryId=13823 Biological Electrochemistry Example Calc. 1: What would be the standard potential of the ½ reaction at a physiologically appropriate pH (7.4)? Q 2 H 2e H2 Q ~ 0.6999V 0 H2 Q 0 . 0592 V 0.6999V 0 log 2 2 Q H 1 0 . 0592 0 V 0.6999V log 2 2 1 H 0.0592 0 2 V 0.6999V log H 2 For standard conditions (1 mole, 1 atm, 25C): Biological Electrochemistry Example Calc. 1 What would be the standard potential of the ½ reaction at a physiologically appropriate pH (7.4)? 0.0592 2 V 0.6999V log H 2 0 V 06999 . V 0 00592 . log H V 06999 . V 0 00592 . log107.4 V 0.6999V 0.0592 7.4 0 V 0.6999V 0 0.43808 V 02619 . Notice that not only Does pH control Structure of proteins It controls the total Energy associated with Many reactions Which is why we emphasize acid base Chemistry over. Which is why we emphasize acid base Chemistry over and over. Which is why we emphasize acid base Chemistry over and over and over. Biological Electrochemistry Example Calculation 2 Watch also the protons +4H+ Cytochrome C Cytochrome c oxidase Fe Containing Heme group H2 O in 4H O2,g 1 2 2e Pump Membrane 2H out Hemeglobin: Oxygen carrier Fe is square planar with 2 more coordination sites top and bottom. One is used for oxygen transport http://www.elmhurst.edu/~chm/vchembook/568globularprotein.html Review: Module 18: Complex Ions Review: Module 17B: Acid Bases Biological Electrochemistry Example Calc. 2: Cytochrome, CyFe2+, reacts with the air we breathe to supply energy required to synthesize adenosine triphosphate (ATP). The body uses ATP as an energy source to drive other reactions. At pH 7.0 the following reduction potentials pertain to this oxidation of CyFe2+ 4e 4 H O 2,g 2 H2 O CyFeaq3 e CyFeaq2 V 082 . V o V 0 0.22V a) What is ΔG for the oxidation of CyFe2+ by air? b) If the synthesis of 1.0 mol ofATP from adenosine diphosphate (ADP) requires a ΔG of 37.7 kJ, how many moles of ATP are synthesized per mole of O2? Biological Electrochemistry Example Calc. 2: At pH 7.0 the following reduction potentials pertain to this oxidation of CyFe2+ 4e 4 H O2, g 2 H2 O CyFeaq3 e CyFeaq2 V o 082 . V V 0 0.22V a) What is ΔG for the oxidation of CyFe2+ by air? 4e 4 H O2, g 2 H2 O 2 aq 4 4CyFe 3 aq CyFe 4e 4 H O2, g 4CyFeaq2 2 H2 O 4CyFeaq3 V o 082 . V V 0.22V 0 V o 0.60V Biological Electrochemistry Example Calc. 2: At pH 7.0 the following reduction potentials pertain to this oxidation of CyFe2+ 4 H O2, g 4CyFeaq2 2 H2 O 4CyFeaq3 V o 0.60V n 4e a) What is ΔG for the oxidation of CyFe2+ by air? G nFV 0 o G 4 96485 0.60 231564 , J 2316 . kJ 0 b) If the synthesis of 1.0 mol ofATP from adenosine diphosphate (ADP) requires a ΔG of 37.7 kJ, how many moles of ATP are synthesized per mole of O2? . molATP 2316 . kJ 615 . molATP 10 37.7 kJ 1molO2 1molO2 Biological “Electrolytic” or Non-spontaneous cell: Photosynthesis Electrons are “pumped” up towards More negative voltage The pump chemistry is Similar (but not identical) to metal ligand crystal Field splitting light “A” students work (without solutions manual) ~ 10 problems/night. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours W – F 2-3 pm Module #21 Electrochemistry Reduction/Oxidation Reaction Coupled to Complexation and Precipitation, more challenging examples (Context Slide 1) Electrochemistry in Mining The Conquest of Mexico In 1550 the Viceroy wrote to the King “In just a few years a large area of forest has been destroyed [near the Taxco silver mines], and it appears that the wood supply will be depleted sooner than the ore. Ordinances have been made regarding the conservation of the forest, and likewise regarding the paths that the Indian workers use for making charcoal, cutting wood, and on the maximum loads that may carry.” Requires a less fuel Intensive method Mercury consumed in New World Spanish silver mines (1560-1820):170,000 tons; USA gold rush (1850-1900): 70,000 tons Amalgamation was introduced in the 1550s in M exico by a Spanish immigrant, Bartolome de M edina, who wrote Dec. 29, 1555 (1): 1. (Context Slide 2) I, Bartolome de Medina do declare that I learned in Spain through discussion with a German, that silver can be extracted from ore without the necessity for s melting it, or refining it, or incurring any other considerable expense. With this information I resolved to come to New Spain. Leaving my home, my wife and my children in Spain, I came to test it, knowing that if I were successful, I would render a great service to Our Lord, and to his Majesty and to all this realm. And having spent much time and money and suffered mental anguish, and seeing that I was not going to be able to make it work, I commended myself to Our Lady and I begged Her to enlighten me and guide me, so that I might be successful and it pleased Our Lady to enlighten me and put me on the right path so that I could make it work. Probert, A. Bartolome de Medina: The Patio P rocess and the Sixteenth Century Silver Crisis. In M ines of Silver and Gold in the Americas. A description of the process 1555. Grind the ore fine. Steep it in strong brine. Add mercury and mix thoroughly. Repeat mixing daily for several weeks. Every day take a pinch of ore mud and examine the mercury. See? It is bright and glistening. As times passes, it should darken as silver minerals are decomposed by salt and the silver forms an alloy with mercury. Amalgam is pasty. Wash out the spent ore in water. Retort residual amalgam; mercury is driven off and silver remains. Solubility Ag2 S 2 Ag S 2 2 3 2 Ag 4S2 O 2 Ag S2 O3 2 3 K f 2 Ksp 1051 2.9 x10 13 2 8.41x1026 1026.9 Complexation 8SO42 16e 32 H 8H2 SO3 8H2 O Reduction Of S 8SO ( to make Complexing agent) 8H2 SO3 16e 8H 4S2 O32 12 H2 O V2o 0.400 S 2 Ss 2e V3o 0.447 2 4 30e 40H 4S2 O32 20H2 O Ss n o log Knet Vnet 0.0592 30 1002 log Knet . 507.7 0.0592 Ag2 S 8SO NET RX o Vnet 1005 . Too complicat d for an exam, Kvoltage,net 10507.7 (Context Slide 2) 2 4 V10 0158 . 30e 40H 2 Ag S2 O3 2 20H2 O S s 3 K Ktotal Knet K f 2 sp 10507.7 1026.9 1050.1 10484.5 Ag2 S 2 Ag S 2 2 4 Ag2 S 8SO Ksp 1051 Insoluble 30e 40H 2 Ag S2 O3 2 20H2 O S s 3 Soluble: driven by oxidation/reduction and complexation K Ktotal Knet K f 2 sp 10507.7 1026.9 1050.1 10484.5 Couple Reactions Example Calculation 1 Good for • Most native silver has long since been used: an exam 2. but we still mine silver dust. 3. How is this economically feasible? 4. How could we get rich with a new process involving CN extraction? What is the voltage, free energy, and K Associated with this reaction? Ag s CN aq O 2,g Ag CN 2 ,aq Ag s CN aq Ag s CN O 2,g aq Ag CN 2 ,aq 1. Balance the equation a. Split into ½ reactions b. Balance each ½ reaction c. Recombine Ag CN 2,aq Ag s 2CN aq Ag CN O2, g ? O2 , g 2 H2 O 2,aq Ag s 2CN aq Ag CN 2,aq 1e 4 Ag s 8CN aq 4 Ag CN 2 ,aq 4 Ag s 8CN aq 4e aq O2 , g 4 Haq 2 H 2 O O2 , g 4 Haq 4e 2 H2 O 4 Ag CN 2 ,aq 4e V o 0.31 V o 123 . O2, g 4 H 4e 2 H2 O o 4 Ag s 8CN aq O2 , g 4 Haq 4 Ag CN 2 ,aq 2 H2 O V 154 . rx The free energy for the reaction is a mere: G = -nFVorx = -4(96485)(1.53) = -5.9x105 J G = -RTln K K = e(-G/RT) = e(-(-590000/(298x8.314)) = e238 = 10238/2.3 = 10103 all you need is: CN (cheap) O2 (air is cheap (an aerator)) Hypothetical Modern Silver/Gold Mine O2 Bulldozer (Context Slide) CNaerator Tibor Kocsis Same process used to recover silver at photography studios, in silver plating. Major cyanide spills: Czech, Elbe River, Jan. 2006; Romania, Tisza River, Nov. 2005; Laos, June, 2005; Ghana River Kubreko, Jan, 2005; China, Papua New Guinea, Ghana, Romania (10 tons Danube River, Mar. 2004), Ghana, Honduras, Nicaragua, China, 2002: Nevada, USA (Context Slide) Using Bugs to Mine Cu from CuS could be an exam question either math or written one Biomining for Gold and Copper in Botswana collect Ksp=10-36 S ox # = -2 CuSs 8Fe 3 4 H2 O 8Fe 2 Cu2 SO42 8H -2 to +6=-8 Need 8 e 8Fe 2 8Fe bugs 3 4x(-2)=-8 S have to have +6 8e Catalytic reagent, supplied courtesy of bugs, Thiobacillus ferridoxin http://www.learner.org/channel/courses/biology/textbook/microb/microb_14.htm “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry Reduction/Oxidation Reactions: Corrosion The Billion $ Question Or: why your taxes will have To always go up Coupled Chemical Equation Challenge Calculation 2 Calculate the formal potential for the reaction to form the initial corrosion product, Fe(OH)3,s reaction at pH 7, 1 atm, 298 K from iron metal and oxygen in the presence of water Given the following information. Fe(OH ) 3 Fe 3 3OH Ksp 6.3x10 38 Fe 2 2e Fes V o 0.44 2 Fe 3 e Fe V 0.771 OH 3 OO 22HHOO44ee 44OH 22 22 o O2 V 0.40 Want a reaction that looks sort of like: Fes O2 , g H2 O Fe OH 3 Balance electrons Start with the oxidation/reduction first V o 0.44 2 Fes 2e Fe 3 Fe 2 e Fe 33 Fes s Fe Fe Fe 3e3e4 V 0.771 V o 0.44 0.771) Coupled Chemical Equation Challenge Calculation 2 Calculate the formal potential for the reaction to form the initial corrosion product, Fe(OH)3,s reaction at pH 7, 1 atm, 298 K from iron metal and oxygen in the presence of water Given the following information. nFV o G o RT ln K Fe(OH ) 3 Fe 3 3OH Ksp 6.3x10 38 4 4 Fe 3 12OH 4 Fe(OH ) 3 3O2 6H2 O 12e 12OH 3 4 Fes 12e 4 Fe Reverse and quadruple 4 1 1 38 K 6 . 3 x 10 sp VOo2 0.40 J 1 G 8.3145 298 K ln 6.3x10 38 mol K 4 o 8.49 x105 J 129.648x104 040 . Go 4.63x105 J V o 0.44 0.771) 129.648x104 0441 . .771 Go 383 . x105 J 4 Fes 3O2, g 6H2 O 4 Fe(OH ) 3 Gnet 170 . x106 J Now we have the reaction need total voltage: Use Rosetta Stone Coupled Chemical Equation Challenge Calculation 2 Calculate the formal potential for the reaction to form the initial corrosion product, Fe(OH)3,s reaction at pH 7, 1 atm, 298 K from iron metal and oxygen in the presence of water Given the following information. nFV o G o RT ln K 4 4 Fe 3 12OH 4 Fe(OH ) 3 4 1 1 38 Ksp 6.3x10 VOo2 0.40 4.63x105 J V o 0.331 383 . x105 J 3O2 6H2 O 12e 12OH 3 4 Fes 4 Fe 12e Gnet 170 . x106 J 4 Fes 3O2, g 6H2 O 4 Fe(OH ) 3 G 170 . x10 V 146 . 4 nF 129.648x10 o net o net 8.49 x105 J 6 Why do we care if this is A highly favorable reaction? Why use it as an example? (Context Slide) Chicago Tribune Week of April 11, 2007 Corrosion Involves several Reactions which result in iron OO removal OO OO Begins at a pit or hole Na+ O H H ClO H H Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe 5 neighbors Which atom is more likely to be removed from the crystal? WHY? Fe FeFe Fe Fe Fe Fe Fe Fe Fe FeFe Fe FeFe Fe Fe Fe 4 neighbors Less bonds to break (Context Slide) Corrosion Involves several Reactions OO OO OO Na+ Cl- O H H O H H OO Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe2+ 2+ 2 2 Fe 2 Fe 4e 2 aq Fe aq xCl FeCl O2 , gas O2 ,aqueous o VFE n x ,aq Kf Khenry (Context Slide) Corrosion Involves several Reactions OO OO Na+ Fe2+ Cl O H O H H H OO Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe 2+ 2 aq 2 Fe 2 Fe Fe 2 4e aq xCl FeCl V n x ,aq O2 , gas O2 ,aqueous O2 2 H2 O 4e 4OH 2 Feaq 2OH aq Fe OH 2 ,s o FE Kf Khenry VOo2 To stop this process prevent access of 1. water 2. NaCl 3. oxygen K sp ,(Context Fe OH 2 Slide) Varnish - need to dry from inside out - requires initial O2 entrance and then sealing otherwise you get a “bubble” OO OO Cl O H O H + H H Na Dry, polymerized unpolymerized Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Use Pb3O4 Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe To carry O2 Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe OO toxic OO Cl O H O H + Dense H H Na barrier CryOy toxic Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe (Context Slide) Third alternative (Context Slide) Corrosion surface coated unevenly with various and multiple salts manipulate to get an even layer of Fe2O3 1. Increase production of Fe3+ 2. Prevent loss of Fe2+ by random walk Electron conducting composite film containing clay orients polymer increases path length of O2 Na+ OO OO O H H Cl- O H H Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe 2+ 2+ Third alternative (Context Slide) Corrosion surface coated unevenly with various and multiple salts manipulate to get an even layer of Fe2O3 2 Fe 2 Fe 1. Increase production of Fe3+ 2. Prevent loss of Fe2+ by random walk 2 4e PAN ox 4 H 4e PAN red PAN red ,1 PAN ox ,2 PAN ox ,1 PAN red , 2 Electron conducting composite film containing clay orients polymer increases path length of O2 Na+ OO OO O H H Cl- O H H Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe 2+ 2+ Third alternative (Context Slide) Corrosion surface coated unevenly with various and multiple salts manipulate to get an even layer of Fe2O3 2 Fe 2 Fe 1. Increase production of Fe3+ 2. Prevent loss of Fe2+ by random walk 2 4e PAN ox 4 H 4e PAN red 10-85 Fe2O3 Ksp Fe(OH)2 Ksp 10-38.8 PAN red ,1 PAN ox ,2 PAN ox ,1 PAN red , 2 2 Fe 2 O2 2 H2 O 2 Fe Fe 3OH 4OH Na+ More insoluble, denser 3 3 Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe3 FeFe Fe Fe Fe Cl- OO OO O H H O H H Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe FeFe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe slow Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe 2 Fe(OH ) 3 Fe 3Fe H2Fe O FeFeFe 2 O3Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe Fe(OH ) 2+ Fe3+ Fe 3+ 2+ “A” students work (without solutions manual) ~ 10 problems/night. Dr. Alanah Fitch Flanner Hall 402 508-3119 [email protected] Office Hours Th- F 2-3:30 pm Module #21 Electrochemistry What you should know 1. Balance oxidation/reduction reactions 2. Convert between V, free energy, and K 3. Calculate standard V of a reaction cell from standard ½ reactions 4. Determine if the cell (reaction) is Galvanic or Electrolytic 5. Calculate V of a reaction at non-standard conditions (change in conc.) 6. Add various electrochemical reactions together (flip reaction change sign) 7. Add various electrochemical and solubility and/or complexation rxs together: This is tricky – need to add in terms of free energy not voltages 8. Be able to explain one example ( energy, biological, environmental, corrosion) of electrochemical reactions.