L31S10_Review+04-09-10

L31S10_Review+04-09-10 - CHEM 1A L32 Review of L21-31 ...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 4/8/2010 CHEM 1A, L32: Review of L21-31  Standard free energy is related to K RT  G° = -RT ln K  Free energy is temperature dependent temperature and vs  G° vs T and ln K vs 1/T as  Exothermic: K as T  Endothermic: K as T as Lecture 30 Topics Free Energy and Equilibrium aA+bB G > 0 K<1 cC+dD G = 0 K=1 G, K  Free energy under non-standard non-standard conditions conditions RT  G = G° + RT ln Q © 2004 M.Kubinec, A. Pines Spontaneous Spontaneous G < 0 K>1 G= RT ln K L32-1 © 2004 M.Kubinec, A. Pines  G = 0 at equilibrium at K = exp ( - RGT) RT L32-2 lnK = Gº Gº - Hº 1 Hº + RT Sº Sº R Gº = Hº -T Sº Sº Free Free Energy and the Reaction Reaction Quotient G(Reactants) G = G(P)  G(R) G(P) G<0 G=0 G>0 G(Products) L32-3 © 2004 M.Kubinec, A. Pines T Hº Sº Hº Sº Hº Sº Hº Sº Hº Sº Hº Sº Hº Sº Hº Sº Q<K Q=K Q>K lnK lnK +- -1/T ++ -+ ° ° RT lnK = GG = GG+ + RT lnQ 0 = L32-4 © 2004 M.Kubinec, A. Pines © 2004 M.Kubinec, A. Pines 1 4/8/2010 CHEM 1A, L32: Review of L21-31 ChemQuiz© 30.4 [xi] Lecture Lecture 20: Kinetic Theory of Gases  gas consists of identical wellgas wellseparated particles (low number (low density) density)  moving in random direction with a moving direction distribution distribution of speeds  move in straight lines between move between collisions collisions  collisions between particles or walls collisions are elastic  no loss of kinetic no energyenergy- conservation of energy © 2001 A.Pines,M.Kubinec,UCB Which is true at t1? A (aq) + 2 B (aq) (aq) C (aq) t1 t A) A) Q > K ©A.Pines,M.Kubinec,UCB B) B) Q = K C) C) Q < K L30-5 L20-7 Pressure, Pressure, Energy and Temperature Temperature PV=  N0mv2 3 Ek T Root-MeanRoot-Mean-Square Speed vrms=  v2 = 3kBT = m 3RT 3RT M = Ek 2 3  N0 (½mv2) = RT ek e k = 3 kB T 2 Per molecule Ek = 3 RT 2 Per mole R=8.31 J/K mol kB=1.381 x 10-23 J/K L20-8 © 2001 A.Pines,M.Kubinec,UCB vrms~ T M L20-9 kB=R/N0 © 2001 A.Pines,M.Kubinec,UCB © 2004 M.Kubinec, A. Pines 2 4/8/2010 CHEM 1A, L32: Review of L21-31 Distribution of Speeds F(v) vrms MaxwellMaxwell-Boltzmann High T vrms Low T v F(v) proportional 2 e Lecture 21 Topics  Real Gases  van der Waals equation van  Corrects for particle volume and Corrects intermolecular interactions  Phase Diagrams  P vs T plot indicates phase vs  Triple point  Critical temperature L20-10 © 2004 M.Kubinec, A. Pines L32-11 Low m High m -E/kBT v (ms-1) © 2001 A.Pines,M.Kubinec,UCB Van der Waals Equation n2 P+a 2 V a: adjust P  for collisions/attractions V - nb =nRT P H 2O S Phase Diagram L Triple Point TTP = 0.01 oC 0.01 PTP = 4.6 torr G Temperature Tc L32-13 b: adjust V  for finite volume of molecules He CO2 H2 O © 2004 M.Kubinec, A. Pines a 0.034 3.59 5.46 b B.P. (K) 0.024 4.2 0.043 0.030 195 373 L32-12 © 2004 M.Kubinec, A. Pines © 2004 M.Kubinec, A. Pines 3 4/8/2010 CHEM 1A, L32: Review of L21-31 Real Gases: Vapor Pressure P(atm) Vapor Pressure Lecture 22 Topics  First Law of Thermodynamics  E = q + w  q = mCs T = heat mC  w = -Pext V = work  Euniv = Esys + Esurr = 0  E is a state function  only difference in final and initial only states states matter  path does not matter © 2004 M.Kubinec, A. Pines Water 1.000 0.031 Tc 100 100 oC 25 25 oC V L32-14 © 2004 M.Kubinec, A. Pines L32-15 First Law of Thermodynamics w:work System (you can t win) Isothermal Isothermal Expansion/Compression Expansion/Compression Pext = F/A + E=q+w E is a state function st Conservation Conservation of E h- Const T : E= H=0 q + ww 0 =- = Expansion wq+ Compression Compression w+ qL32-17 - + q:heat Euniv = Esys + Esurr = 0 surr L32-16 © 2004 M.Kubinec, A. Pines Surroundings © 2004 M.Kubinec, A. Pines © 2004 M.Kubinec, A. Pines 4 4/8/2010 CHEM 1A, L32: Review of L21-31 Adiabatic Adiabatic Expansion/Compression Expansion/Compression Pext = F/A Lecture 23 Topics  Thermochemistry: Enthalpy Thermochemistry:  H > 0, Endothermic, E absorbed  H < 0; Exothermic, E released 0;  Standard enthalpies of formation  H°f = 0 for elements in standard state q=0: hExpansion w<O E<O © 2004 M.Kubinec, A. Pines E=w Compression w>O E>O L32-18  Standard state = 1M, 1 atm and specified T Standard  H°rxn = Hf°(products)- Hf° (reactants) (products)L32-19 © 2004 M.Kubinec, A. Pines Thermochemistry aA+bB q= H cC+dD H>0 H<0 Standard Enthalpy Change Reactants Hfº(R) Elements Elements in Standard Standard States Hº = © 2004 M.Kubinec, A. Pines Products Hfº(P) H System Endothermic: q > 0 E Heat is absorbed Heat is released System Exothermic: q < 0 qSurroundings © 2004 M.Kubinec, A. Pines 0 Standard Standard States: Hº 1M, 1atm, 25ºC L32-20 Hfº(P)  Hfº(R) L32-21 © 2004 M.Kubinec, A. Pines 5 4/8/2010 CHEM 1A, L32: Review of L21-31 Standard Standard Enthalpies of Formation Formation (kJ mol-1) H2(g) O2(g) (g) C(s) Al(s) Fe(s) Fe(s) N2(g) Lecture 24 Topics -278 -1274 -824 -1676 L32-22 0 +218 +249 +473 C(g) CO2(g) H20(l) H20(g) +717 -394 -286 -242 CH3CH2OH OH (l) (l) H(g) O(g) N(g) C6H12O6 (s (s )  Heat Capacity Heat  energy needed to raise 1 g (or 1 mol) energy of of substance by 1°C 1°  Bomb Calorimetry Bomb  Method of measuring H for reaction Method for  Heat flow measured by T of H2O Heat of  Conservation of E: qrxn = -(qwater + qcal) Conservation © 2004 M.Kubinec, A. Pines L32-23 Fe2O3 (s) (s) Al2O3 (s) (s) © 2004 M.Kubinec, A. Pines Heat Capacity Heat capacity = E required to raise the T of required of an object by 1 degree. Varies from degree. Varies material material to material. Specific heat capacity (cs) (J K-1g-1)  Energy needed to heat 1 g of substance by 1 degree. degree. q=mc T Molar heat capacity (cm) (J K-1 mol-1)  Energy needed to heat 1 mole of substance Energy of q = n cm T by by 1 degree. © Pines, Kubinec,Nitsche 2006 L24-24 Heat Capacities Substance Elements cs (J g-1 K-1) 0.902 0.720 0.451 0.385 0.129 4.70 4.184 2.46 2.42 2.06 0.861 0.598 cm (J mol-1 K-1) (J 24.3 8.65 25.1 24.4 25.4 80.1 75.3 112. 149. 37.1 132. 72.3 Al(s) C (graphite) Fe (s) Cu (s) Au (s) NH3(l) H2O (l) C2H5OH (l) (CH2OH)2 (l) H2O (s) CCl4 (l) CCl2F2(l) Compounds Compounds © Pines, Kubinec,Nitsche 2006 L24-25 © 2004 M.Kubinec, A. Pines 6 4/8/2010 CHEM 1A, L32: Review of L21-31 Bomb Calorimeter Heat Heat flow is monitored by of measuring T of the water. water. (Twater = Tbomb) ignition wires Lecture 25 Topics  Enthalpy of reactions from Bond Enthalpy Energies  H° = Ex-y(reactants)- Ex-y(products) (reactants)  Bond enthalpies are all positive, requires requires E to break them Conservation Conservation of energy: energy: qreaction + qbomb + qwater or 0 = qreaction = qbomb + qwater Insulated chamber © 2004 M.Kubinec, A. Pines water Steel bomb filled with O2, immersed in Sample dish water with burning L32-26 sample © 2004 M.Kubinec, A. Pines L32-27 Bond Bond Energies and Reaction Reaction Enthalpies Atoms Ex-y(R) E Average Average Bond Enthalpies (kJ· (kJ·mol-1) CH H (g) CO2 Cl (g) Cl Cl H20 O O- (l) HO=(g) 20 O L32-28 436 +717 -242 394 146 -286 497 -242 C (g) CC CO2 (g) C=C H20 C C (l) +717 348 -612 394 -286 838 413 -242 C (g) CO CO O2 H H20(g) +717 360 -463 394 -286 431 946 -242 L32-29 - Ex-y(P) Reactants Elements ° H f° © 2004 M.Kubinec, A. Pines H°= Ex-y(R) - Ex-y(P) f Products Compounds H ) Cl Cl NN H20 (g) CH H20 (g) © 2004 M.Kubinec, A. Pines © 2004 M.Kubinec, A. Pines 7 4/8/2010 CHEM 1A, L32: Review of L21-31  Second Law of Thermodynamics Second  Suniv = Ssurr + Ssys 0  Suniv > 0; Spontaneous, Irreversible  Suniv = 0; Reversible, Equilibrium 0;  Suniv < 0; Not Possible  Entropy  Measure of disorder Measure qrev Sº =  T  S = kB ln W; W = microstates © 2004 M.Kubinec, A. Pines L32-30 Lecture 26 Topics The Second Law (You can t break even) For any For any process: Suniv = Ssys + Ssurr 0 > 0 : Spontaneous, Irreversible = 0 : Reversible, Equilibrium Reversible, < 0 : Not Possible © 2004 M.Kubinec, A. Pines L32-31 Isothermal Isothermal Expansion/Compression Expansion/Compression Pext Lecture 27 Topics  Gibbs Free Energy  G ° reports on the entropy of the reports on universe using what is known about the the system!!!  G ° = H ° -T S ° Const T : h- E= H=0 q + ww 0 =- = Expansion w<0 q>0 S>0 © 2004 M.Kubinec, A. Pines Compression w>0 q<0 S<0 L32-32 © 2004 M.Kubinec, A. Pines L32-33 © 2004 M.Kubinec, A. Pines 8 4/8/2010 CHEM 1A, L32: Review of L21-31 Gibbs Free Energy G = H - TS Gº = Hº -T Sº Spontaneous Process H S G Free Energy Space G = H -T S H>0 H>0 H<0 S<0 S0 S >> 0 Endothermic Endothermic Exothermic More order Less order Less order No T Low T H High T All T S G °< O Gº = © 2004 M.Kubinec, A. Pines Gfº(Products)  Gfº(Reactants) L32-34 © 2004 M.Kubinec, A. Pines L32-35 Free Free Energy and Reactions K (s) + H20 (l) (s) (l) H2O(l) + ½O2(g) O(l) ½O AlBr3 (s) (s) Al (s) Al (s) + K+ (aq) (aq) + OH- (aq) + ½ H2 (g) (g) Lecture 28 Topics G -++ -+ +++ --+ H S  Law of Mass Action  For aA + bB cC + dD For bB cC dD  Q = [C]c[D]d = K (T) at equilibrium [A]a[B]b  Q < K: Products favored  Q > K: Reactants favored © 2004 M.Kubinec, A. Pines L32-37 H2O2(l) 3/2 3/2 Br2 (l) (l) 2 Mg (s) + CO2 (s) Mg (s) (s) © 2004 M.Kubinec, A. Pines 2 MgO (s) + C (s) MgO (s) (s) L32-36 © 2004 M.Kubinec, A. Pines 9 4/8/2010 CHEM 1A, L32: Review of L21-31 Approach Approach and Maintenance H2,O2 Equilibrium Equilibrium Unstable ChemQuiz© 28.4 For For the reaction: I2(s) I2 (g) what what happens to the vapor vapor color intensity when T is is raised raised ? B) A) A) Increases B) Same C) Decreases C) © 2001 A.Pines,M.Kubinec,UC L28-39 Stable Pi,, [Xi] i [X Stable H2O Monotonic © 2004 M.Kubinec, A. Pines Clock Oscillatory Chaotic L32-38 Lecture 29 Topics  Le Chatelier s Principle Le  A system in equilibrium subjected to system a stress will react in a direction to reduce reduce this stress Multiple Multiple Equilibria Le Châtelier s Principle A system in equilibrium subjected to a system stress will react in a direction that tends tends to reduce the stress Q=K Q>K Q=K V P Q © 2004 M.Kubinec, A. Pines L32-41 © 2004 M.Kubinec, A. Pines L32-42 © 2004 M.Kubinec, A. Pines 10 4/8/2010 CHEM 1A, L32: Review of L21-31 Review Complete © 2004 M.Kubinec, A. Pines L32-43 © 2004 M.Kubinec, A. Pines 11 ...
View Full Document

This note was uploaded on 04/24/2010 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at Berkeley.

Ask a homework question - tutors are online