CVEN 5424 Environmental Organic Chemistry Lecture 4 – Vapor Pressure Estimation

Announcements Reading  Chapter 4, Vapor pressure Problem sets PS 1 due today PS 2 out today Office hours – next week (because of travel) Monday 9-10 am Tuesday 11:30 am-1 pm Office hours – semester Tuesday 11:30 am-1:00 pm Wednesday 9-10 am

Announcements Room SEEC C326 (RASEI Fellows Conf Rm) – this week SEEC S298 – rest of the semester, starting Jan 26 Lectures lecture Tues Jan 26 no lecture Thur Jan 28 double up Tues Jan 26, 8:30 am or 11:30 am double up Tues Feb 2, 8:30 am or 11:30 am

Vapor Pressure

 Clayperon I  For the phase transition 1  2,   12 H is the change in molar enthalpy  measures intermolecular attraction   12 V is the change in molar volume  measures randomness Benoît Paul Émile Clapeyron

Vapor Pressure solid liquid gas 1 2 3

Vapor Pressure  Solid-liquid   12 H =  fus H  fus H is large   12 V =  fus V  fus V is small   fus H /T  fus V is very large; so is dp/dT solid liquid gas 1 1

Vapor Pressure  Liquid-gas   12 H =  vap H  vap H is large (  vap H >  fus H)   12 V =  vap V  vap V is large (  vap V >>  fus V)   vap H /T  vap V is small; so is dp/dT solid liquid gas 2 2

Vapor Pressure  Solid-gas   12 H =  sub H  sub H is very large (=  fus H +  vap H)   12 V =  sub V  sub V is large (  fus V +  vap V) ~  sub V   sub H/T  sub V is “medium”; so is dp/dT solid liquid gas 3 3

Vapor Pressure Hypothetical liquids –“subcooled liquid” –hypothetically –hypothetically not having to pay melting costs to get solid to vaporize –will be important for determining vaporization of organic compound from water solid liquid gas TmTm

Vapor Pressure Hypothetical liquids –“superheated liquid” –hypothetical –hypothetical vapor pressure of a liquid above its boiling point solid liquid gas 1 atm TbTb

Vapor Pressure  Clayperon II  Enthalpy  breaking bonds in condensed phase  essentially no bonds formed in vapor phase  Entropy  increase in randomness in gas phase  bonding results in orientation in condensed phases

Vapor Pressure  Clayperon II  Enthalpy  van der Waals  varying electron distribution: dipole-induced dipole, dipole- dipole  relevant for all compounds  characteristic of apolar or nonpolar compounds  major contributor to  12 H

Vapor Pressure  Clayperon II  Enthalpy  monopolar  electron donor OR electron acceptor character  donors: ether (-C-O-C-), keto (>C=O)  acceptors: aromatic ring with electronegative substituents  minor contributor to  12 H; a few kJ mol -1

Vapor Pressure  Clayperon II  Enthalpy  bipolar  electron donor-acceptor, or hydrogen bonding, character  hydroxyl (-OH), carboxyl (-COOH)  amino (-NH 2 )  sulfhydryl (-SH)  significant contributor to  12 H; kJ mol -1  monopolar and bipolar = polar

Vapor Pressure  Clayperon II  Entropy  solid  liquid  static in solid; some interactions in liquid  liquid  gas  some orientation in liquid; none in gas  molecular characteristics  allows translation – all molecules  allows rotation – non-symmetric molecules  allows flexing – molecules with chains

Vapor Pressure alkane T b (  C) log p* (bar)  vap,sub H (kJ mol -1 ) T  vap,sub S (J mol -1 ) methane, CH ethane, C 2 H propane, C 3 H butane, C 4 H pentane, C 5 H hexane, C 6 H heptane, C 7 H octane, C 8 H nonane, C 9 H decane, C 10 H hexadecane, C 16 H

Vapor Pressure 25°C

Vapor Pressure

 What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D

Vapor Pressure  What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D

Vapor Pressure  What explains the decrease in vapor pressure for alkanes of increasing chain length? A. hydrogen bonding increases with chain length B. van der Waals forces increase with chain length C. electron donor-acceptor (polar) forces increase with chain length D. increase in entropy increases with chain length E. both B and D entropy does increase with chain length, but an increase in entropy favors an increase in vapor pressure

Vapor Pressure compoundstructure T b (  C)  vap H (T b ) (kJ mol -1 )  (D) benzene chlorobenzene ,2-dichlorobenzene ,3-dichlorobenzene ,4-dichlorobenzene ,2,3-trichlorobenzene ,2,4-trichlorobenzene ,3,5-trichlorobenzene ,2,3,4-tetrachlorobenzene ,2,3,5-tetrachlorobenzene ,2,4,5-tetrachlorobenzene pentachlorobenzene hexachlorobenzene

Vapor Pressure  What is another name for this compound, 1,4- dichlorobenzene? A. chlorobenzene B. p-chlorobenzene C. p-dichlorobenzene D. p-dichlorobenzoic acid E. Paracide

Vapor Pressure  What is another name for this compound, 1,4- dichlorobenzene? A. chlorobenzene B. p-chlorobenzene C. p-dichlorobenzene D. p-dichlorobenzoic acid E. Paracide

Vapor Pressure

 What kind of interaction is responsible for the increase in boiling point and enthalpy of vaporization in the series of benzene, chlorobenzene, and o-dichlorobenzene? A. van der Waals B. polar (electron donor-acceptor) C. hydrogen bonding

Vapor Pressure  What kind of interaction is responsible for the increase in boiling point and enthalpy of vaporization in the series of benzene, chlorobenzene, and o-dichlorobenzene? A. van der Waals B. polar (electron donor-acceptor) C. hydrogen bonding

Vapor Pressure Data Vapor pressure from data (e.g., CRC Handbook) ln p (bar) 1/T (K -1 ) higher T lower TmTm solid liquid subcooled liquid

ln p (bar) 1/T (K -1 ) TmTm p iL *  vap H/R  sub H/R p iL * p iS *  sub H =  vap H +  fus H

Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s

Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s

Vapor Pressure Data  Example  determine the vapor pressure of tetrachloroethene at 25  C using vapor pressure data from the CRC*  T m = -19  C = 254 K  T b = 121  C = 394 K *or some other source of P-T data T (  C) p L,S (mm Hg) -20.6s

 Example  ln p vs. 1/T Vapor Pressure Data T (C) T (K) 1/T (1/K) ln p (bar) p (bar) p (mm Hg)

Vapor Pressure Data  Example  enthalpy of vaporization

Vapor Pressure Data  Example  vapor pressure at 25  C

Vapor Pressure Data  Example  vapor pressure at 25  C

Vapor Pressure Data  Example  vapor pressure at 25  C

Vapor Pressure Estimation  Estimating vapor pressure of a liquid – where we are headed:

Vapor Pressure Estimation  Estimating vapor pressure of a solid – where we are headed:

Next Lecture  Vapor Pressure  Aqueous Solubility  start reading Chapter 5