Chemistry 163B. Concluding Factoids. and. Comments

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1 Chemistry 163B Concluding Factoids and Comments 1

2 neuron, resting potential

resting potential and Nernst Equaiton major source of potential: [K + ] outside (C out ) [K + ] inside (C in ) Q 0 [ K ] [ K ] RT nf RT nf inside outside ln Q The computed number is a little higher

3 resting potential and Nernst Equaiton major source of potential: [K + ] outside (C out ) [K + ] inside (C in ) Q 0 [ K ] [ K ] RT nf RT nf inside outside ln Q The computed number is a little higher than the quantity measured in experiments (-70 mv) but all the factors in this complex physical process have been accounted for. [ K ] ln Q.0569ln [ K ] inside outside 140 mm.0569ln 0.086V 5 mm 3

4 vocabulary Gibbs-Duhem the partial molar quantities do not vary independently 4

5 Gibbs-Duhem what are X EtOH V n EtOH EtOH V HO XHO n T, P, n EtOH T, P, n HO HO V n a a T, P, n a T, P, n b and V n when a and b form an ideal solution? b b do ideal solutions obey the Gibbs-Duhem relation? 5

6 non-ideal solutions 6

7 benzene-toluene, quite ideal (similar to Fig 9. E&R)!! P X P P X P ( ) ( ) A A A B B B P X P P P ( ) total A A B B 7

8 ideal solution: T vs X (P=1 atm) for solution-vapor equilibrium toluene (b.p.=383.78) + benzene (b.p.=353.5) tol+ben (vapor) [f remaining =] tol+ben (solution) [f remaining =] 8

9 non-ideal solutions: azeotrope Definition[s]: constant boiling liquid solution where the mole fraction of each component is the same in the liquid (solution) as the vapor X X ( ) ( v) i i boiling point of azeotrope may be higher or lower than of pure liquids 9

from Raoult s Law: smaller forces between components than

10 non-ideal solutions: positive deviations from ideal solution (E&R pp 14-18) CS ( ) + (CH 3 ) CO ( ) positive deviations from Raoult s Law: smaller forces between components than within components total pressure greater than ideal solution 10

11 acetone-carbon disulfide: positive deviation low boiling azeotrope 11

$low boiling azeotrope weaker between component forces (A B) (than A A, B B) fractional distillation leads to constant boiling azeotrope in vapor and (in pot$

12 low boiling azeotrope weaker between component forces (A B) (than A A, B B) fractional distillation leads to constant boiling azeotrope in vapor and (in pot after azeotrope boils off) (X A ) initial > (X A ) azeotrope pure A (X A ) initial < (X A ) azeotrope pure B 1

13 Water-Ethanol Mixture For the water-ethanol mixture, the azeotrope concentration corresponds to ~95% of ethanol in the mixture. This is the limit that can be reached by distillation of a less-alcohol-rich mixture. 13

14 non-ideal solutions : negative deviations from ideal solution CHCl 3 ( ) + (CH 3 ) CO ( ) negative deviations from Raoult s Law: greater forces between components than within components total pressure lower than ideal solution 14

15 acetone-chloroform: negative deviation high boiling azeotrope 15

$high boiling azeotrope stronger between component forces (A B) (than A A, B B) fractional distillation leads to pure component in vapor until solution (pot)$

16 high boiling azeotrope stronger between component forces (A B) (than A A, B B) fractional distillation leads to pure component in vapor until solution (pot) reaches azeotrope composition (X A ) initial > (X A ) azeotrope pure A (X A ) initial < (X A ) azeotrope pure B 16

17 simple distillation 17

18 simple distillation (one evaporation; T bp varies as X changes) T bp X add heat ( solution) benzene decreases increases gradually ( solution) X benzene ( v) X benzene X benzene 18

19 fractional distillation 19

7 II III. condense X benzene.7 T bp 359.

20 Fractional Distilation vapor composition I. start with mixture T bp 366 II. vapor X v benzene.7 II III. condense X benzene.7 T bp liquid composition I III IV IV. evaporate vapor X v benzene.88 V. etc,... VI. apporaches X benzene =1 0

21 T vs progress for a distillation (top of column) 1

22 Electrolytes and Debye-Huckel Theory

23 activity coefficients for ions (HW9 #58) BaCl s Ba aq Cl aq a a ( ) ( ) ( ) sp BaCl ( s) 1 Ba ( aq) Ba a K a Cl ( aq) Cl Ba ( aq) Cl ( aq) a BaCl ( s) Ba Cl a cannot but only determine and independently Ba Cl Ba Cl K sp 3 Ba 1M 1 (1) Cl 1M sp 3 K Ba Cl 3

24 Debye-Hückel Theory a priori calculation of activity coefficients,, for ions expect < 1 since ions not independent [effective concentration reduced; a < c ] is calculated as work done to bring other charges to region surrounding ion in question the result is ln where z and z 1 z z T 3 1 depends on the solvent's dieelectric constant and other physical constants are the (interger) charges on the cation and anion and I= mz i i is the ionic strength of i I [ E& R: Eqn 10.3 with from Eqn. 10.9] the solution, m i is molal concentration of ion 4

25 Debye-Hückel Theory ln where z and z 1 z z T 3 1 depends on the solvent's dieelectric constant and other physical constants are the (interger) charges on the cation and anion and I= mz i i is the ionic strength of i I [ E& R: Eqn 10.3 with from Eqn. 10.9] the solution, m i is molal concentration of ion 1 1 log z z I for water solvent at 98.15K ln z z I (E&R eqn 10.33) 1 I= mi zi mi zi ionic strength i 5

26 observations: thermo heat Count Rumford, 1799 observed water turning into steam when canon barrel was bored work heat 6

27 1 st law du dq PdV dw du 0 dh dq VdP dw other other 7

28 observations: mechanical efficiency of steam engine Sadi Carnot, 184 efficiency of engines 8

29 nd Law microstates and disorder ds ds fficiency S dq T dq T ds 0 1 rev UNIVERSE T T 0 du TdS PdV dw dh TdS VdP dw L H other other 9

Applications How does knowledge about efficiencies of steam engines, mechanical systems, etc, relate to processes in chemical, biological, and geological systems? ANSWERED BY: J. W.

30 Applications How does knowledge about efficiencies of steam engines, mechanical systems, etc, relate to processes in chemical, biological, and geological systems? ANSWERED BY: J. W. Gibbs- arguably the frist great American scientist who combined the concepts of heat and entropy and proposed [Gibbs] Free Energy, G, a thermodynamic state function that leads to a whole spectrum of applications 30

31 Free Energy and Equilibrium G H T S G T, P T, P T, P T, P T, P S H T T surroundings dg SdT VdP dw da SdT PdV dw S S other other T, P system 31

32 Applications 3

33 quantitative-deductive mathematical abilities H dh TdS VdP dn n i i T, P, n j ni i Maxwell-Euler V S P, n S, n all T P all / T T reac T P / T P H T H T reac ln K T eq P H RT o reac 33

34 Final Exam Conceptual and analytical math from throughout term Problems concentrate on material since last exam Ideal Solutions and corrections for non-ideality Phase equilibria and phase diagrams one-component, relationship of T and P for one component equilibrium two-component (solid solution and solution vapor ) Colligative properties (HW9) Electrochemistry (HW9) Φ and ΔG, Δ Three cells Vocabulary from concluding factoids BRAIN POWER 34

35 Chemistry 163B Winter 014 help sessions Finals Prep 35

36 the lifetime warranty chem

37 the warranty From: Gene Switkes To: XXXXXXXXXX Sent: Mon, February 15, :51:17 AM Subject: Re: Question from former student Hi David, Good to hear from you don't know if the chem 101 warranty is still valid [just joking]. [answered question about disorder] >Eugene Switkes, 37

38 chem 163B warranty Date: Mon, 15 Feb :48: (PST) From: David XXXX XXXXXXXXXXX Subject: Re: Question from former student Very helpful, thanks. By the way, I had 163 with you, not and I distinctly recall that you said that the 163 warranty NEVER expires... Cheers, David 38

39 FINIS (except) 39

Outline of the Course

Outline of the Course 1) Review and Definitions 2) Molecules and their Energies 3) 1 st Law of Thermodynamics Conservation of Energy. 4) 2 nd Law of Thermodynamics Ever-Increasing Entropy. 5) Gibbs Free