Thermodynamic Principles. Environmental Organic Chemistry ESE-CH

Transcription

1 Thermodynamc Prncples Envronmental Oranc Chemstry ESE-CH

2 Chemcal Potental What s chemcal potental? J.W. Gbbs Chemcal potental s the Gbbs free enery added for each added mole of a component () of the system é ê ë G n ù ú û T, Pn, j¹ º µ -1 (kj mol )

3 Glbert N. Lews Fuacty A measure of chemcal potental A tendency to flee A chane n chemcal potental related to a chane n vapor pressure (dp ) ( dµ ) = V dp T n Fuacty s a measure of a chemcal potental n the form of 'adjusted pressure'. It reflects the tendency of a substance to prefer one phase (lqud, sold, or as) over another, and can be lterally defned as the tendency to flee or escape. The phase wth the lowest fuacty wll be the most favorable, and wll have the lowest Gbbs free enery. Fuacty s expressed n unts of pressure. 1 atm = 101,325 Pa bar 760 torr

4 Fuacty s a state functon of matter at a fxed temperature. It only becomes useful when dealn wth substances other than an deal as. For an deal as, fuacty s equal to vapor pressure. Under low pressures and hh temperatures some substances approach deal behavor, no substance s truly deal, so fuacty s used to descrbe non-deal ases, lquds and solds.

5 é G ù ê ú ë n û T, Pn, j¹ º µ -1 (kj mol ) ( dµ ) = V dp T n

6 Fuacty of Gases Assumn an deal as V PV = nrt = n Interatn wth respect to a defned standard state (e..,! 0, P 0 ): RT P ( dµ ) = V dp T n é P ù = 0 + RT ln ê ú P 0 ë û µ µ

7 Fuacty of Gases For non-deal ases (hher concentratons, ntermolecular nteractons) and as mxtures é f ù = 0 + RT ln ê ú f 0 ë û µ µ For an deal as 0 lm 1 P = f P

8 Fuacty of Gases Ideal as: f = P Non-deal as: f =q P Ideal as mxture: f = xp Non-deal as mxture: f =q xp

9 Fuacty of Lquds Ideal lqud: f = P l 0 () Non-deal lqud: f = P l 0 () Ideal lqud mxture: f = xp l 0 () Non-deal lqud mxture: f = xp l 0 ()

10 Molecular formula CCl 4 Molar mass /mol Appearance colorless lqud ether-lke odor /cm 3, lqud Densty cm -3 at -186 C (sold) cm -3 at -80 C (sold) Meltn pont C (250 K) Boln pont C (350 K) Solublty n water m L -1 at 25 C Solublty soluble n alcohol, ether, chloroform, benzene lo K OW 2.64 Vapor pressure kpa at 20 C Refractve ndex (n D )

11 Fuacty of Solds Ideal sold: Non-deal sold: Ideal sold mxture: Non-deal sold mxture: f = P s f = P s 0 () 0 () f = xp s 0 () f = xp s 0 ()

12 Substance P v (Pa) P v (bar) P v (mmh) T ( C) Tunsten 100 Pa Ethylene lycol 0.5 kpa Propanol 2.4 kpa Water 2.4 kpa Ethanol 9 kpa Methyl sobutyl ketone kpa Freon kpa Acetaldehyde 98.7 kpa Helum 100 kpa Butane 220 kpa Formaldehyde kpa Carbonyl sulfde MPa Propane 2.2 MPa Oxyen 54.2 MPa Ntroen 63.2 MPa

13 Propertes Molecular formula C 12 H 4 Cl 4 O 2 Molar mass /mol Densty 1.8 cm 3 Meltn pont 305 C, 578 K, 581 F lo K o/w 6.8 Vapor pressure 2,3,7,8-Tetrachlorodbenzodoxn mm H

14 Vktor Yushchenko, Former Presdent of the Ukrane, Posoned wth Doxn durn Electon Campan October 2004

15

16

17

18 Germany has had to halt sales of poultry pork and es from more than 4,700 farms after anmal feed was found to contan doxns. The anmal feed 'contaned 78 tmes approved amount of doxn reported on

19 Polydmethylsloxane (PDMS) S(CH ) Cl + n H O [S(CH ) O] + 2n HCl n

20 Global concentratons of cyclc volatle methyl sloxanes (n/m 3 ). Global concentratons of lnear volatle methyl sloxanes (n/m 3 ).

21

22 Sold Gas Vapor Pressure p-dchlorobenzene napthalene 1,4-Dchlorobenzene (paradchlorobenzene, p-dcb, PDB) s an oranc compound wth the formula C 6 H 4 Cl 2. Ths colourless sold has a stron odor. p-dcb s used a pestcde and a deodorant, most famously n mothballs n whch t s a replacement for the more tradtonal naphthalene. p-dcb s also used as a precursor n the producton of the polymer poly(p-phenylene sulfde).

23 1,4-dchlorobenzene 1,4-dchlorobenzene s used as an ar freshener, deodorzer n urnals and as a moth and brd repellent. In 1990, t was estmated that 3500 tons per year were ben used n Canada alone. Cl Cl - Lo P o = 2.8 (atm)

24 Napthalene Propertes Molecular formula C 10 H 8 Molar mass mol -1 Appearance Densty 1.14 cm -3 Meltn pont Boln pont Whte sold crystals/flakes, stron odor C, 353 K 218 C, 491 K Solublty n water 30 m L -1

25 Cedarwood (E)-5-(prop-1-enyl)benzo[d][1,3]doxole 4-Allyl-2-methoxyphenol 5-(2-propenyl)-1,3-benzodoxole (2R,4aR,8aS)-Decahydro-8-methylene- alpha,alpha,4a-trmethyl-2- naphthylmethanol

26 Reference and Standard States Gases: 0 é f ù é 0 f ù µ = µ + RT ln RT ln ê µ 0 ú = + ê ú ë f û êë f pure as úû 0 µ ln q = + RT [ x ] Lquds: Solds: é f ù µ = µ + RT ln = µ + RT ln x êë úû [ ] 0 0 ê ú f purelqud é f ù µ = µ + RT ln = µ + RT ln x êë úû [ ] 0 0 ê ú f pure sold

27 Non-dealty deal [ x ] = 0 + RT ln µ µ nondeal } a An deal soluton or deal mxture s a soluton n whch the enthalpy of soluton (or "enthalpy of mxn") s zero; the closer to zero the enthalpy of soluton s, the more "deal" the behavor of the soluton becomes. Lkewse, an deal mxture s one n whch the actvty coeffcents (whch measure devaton from dealty) are equal to one.

28 Attractve Forces van der Waals force Dpole dpole nteractons Hydroen bonds The reater the attractve forces between molecules, the hher s the boln pont of the compound

29 van der Waals Forces The boln pont of a compound ncreases wth the ncrease n van der Waals force

30 Dpole Dpole Interactons Dpole dpole nteractons are stroner than van der Waals force but weaker than onc or covalent bonds

31 Hydroen Bondn

32 Entropy of a molecule s ts freedom to twst and turn (orentaton) move electrons around ts structure (confuraton) be random n space (translaton) Enthalpy of a molecule s a measure of the molecule s attractons to ts surroundns (ntermolecular) tself (ntramolecular)

33 Phase Transfer Set chemcal potentals of compound n the two phases equal: A 1 A 2 é 0 f ù µ 1 1 = µ pure A + RT ln ê ú êë f pure úû é 0 f ù µ 2 2 = µ pure A + RT ln ê ú êë f pure úû f we set µ = µ (equlbrum), 1 2 f = f 1 2

34 Lqud to Ar Transfer Set fuactes of compound n the lqud and as equal: A lqud A as l xp l 0 () l = q xp A A A A A T q 1 l xp l 0 () l = xp A A A A T f lqud A =» f as l xp l 0 () l = P A A A A x P = xp A A T A n = A å n j j

35 In a small workshop at 25 o C, pant thnner s used to clean pant brushes Pant Thnner (a solvent) contans 1 vol% p-xylene n mneral sprts. Assumn that all of the pant thnner does not volatlze at equlbrum, what s the concentraton of p-xylene n the ar of workshop?

36 Model: Chem3D XML n Boln Pont = Kelvn Crtcal Pressure = Bar Crtcal Temperature = Kelvn Crtcal Volume = cm 3 /mol Gbbs Free Enery = kj/mol Heat Of Formaton = kj/mol Henry's Law Constant = 0.51 Ideal Gas Thermal Capacty = J/(mol-K) Lo K ow = 3.15 Meltn Pont = K Mol Refractvty = cm 3 /mol Vapor Pressure = Pascal Water Solublty = m/l

37 CAS Number : Chemcal Name : p-xylene Molecular Formula: C 8 H 10 Molecular Weht : Meltn Pt : 13.2 C Boln Pt : C Water Solublty:162 m/l or M lo K ow (octanol-water): 3.15 Vapor Pressure: 8.84 mm H Henry's Law Constant: atm-m 3 /mole OH Rate Constant: cm 3 /molecule-sec T = K or 25 o C

38 lo P v p-xylene Vapor Pressure vs T T

39 P (mm H) Example T n C Acetone Naphtha Toluene p-xylene Methyl ethyl ketone (MEK) Dmethylformamde (DMF) Whte Sprts Turpentne

40 Solvent - Naptha Full rane naphtha s defned as the fracton of hydrocarbons n petroleum boln between 30 C and 200 C. It conssts of a complex mxture of hydrocarbon molecules enerally havn between 5 and 12 carbon atoms. It typcally consttutes 15 30% of crude ol, by weht. Lht naphtha s the fracton boln between 30 C and 90 C and conssts of molecules wth 5 6 carbon atoms. Heavy naphtha bols between 90 C and 200 C and conssts of molecules wth 6 12 carbons.

41 Lqud to Ar Transfer Set fuactes of compound n the lqud and as equal: A lqud A as l xp l 0 () l = q xp A A A A A T q 1 l xp l 0 () l = xp A A A A T f lqud A =» f as l xp l 0 () l = P A A A A P = xp A A T x A x l A n = A å n j j l na = å n j l j

42 p-xylene Vapor Concentraton? f l p-xyl = f p-xyl l x l P 0 () l = q x P p-xyl p-xyl p-xyl A p-xyl T q p-xyl» 1 l x l P 0 () l = x P p-xyl p-xyl p-xyl p-xyl T l x l P 0 () l = P p-xyl p-xyl p-xyl p-xyl l p - xyl l x p - xyl =??! 0.01 x l A l na = å n j l j

43 P 0 p-xyl () l Vapor Pressure vs. T T CAS Number: Formula: C 8 H 10 CA Index Name: 1,4-dmethylbenzene P 0 p xyl ( l) == 7.94 torr - T = 25 C

44

45 Extreme Case Pure Lqud p-xylene P 0 p-xyl () l atm n/v = P/RT mol / L ar T 298 K R L-atm mol -1 K -1 P 0 p-xyl () l 7.94 torr [p-xylene] mol L -1 [p-xylene] ppmv

46 Actvty Coeffcents at Infnte Dluton of Alkanes, Alkenes, and Alkylbenzenes n 4-Methyl-n-butylpyrdnum Tetrafluoroborate T T T benzene (313.68) (322.99) (333.36) (343.79) toluene (313.79) (322.99) (333.24) (343.55) ethylbenzene (313.69) (322.99) (333.24) (343.55) o-xylene (313.68) (322.93) (333.23) (343.58) p-xylene (313.72) (323.47) (333.25) (343.57) m-xylene (313.67) (322.93) (333.23) (343.57) -propylbenzene (313.73) (322.94) (333.23) (343.58) t-butylbenzene (313.73) (322.95) (333.23) (343.58) T

47 p-xylene n the Workshop Ar atm ppmv P 0 p-xyl () l NA l p - xyl =?? x l p - xyl! 0.01