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  • 8/9/2019 VI. Thermochem Dinamic

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    1Chapter VI:Chapter VI:THERMOCHEMISTRYTHERMOCHEMISTRY

    ThermodynamicsThermodynamicsThe study of Heat and WorkThe study of Heat and Work

    and State unctionsand State unctions

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    2

    Ener!y " ChemistryEner!y " Chemistry

    Ener!y " ChemistryEner!y " Chemistry

    ENERGYENERGYis the capacity tois the capacity todo work or transfer heat.do work or transfer heat.

    HEATHEATis the form of energyis the form of energythat flows etween 2 o!ectsthat flows etween 2 o!ects

    eca"se of their difference ineca"se of their difference intemperat"re.temperat"re.

    #ther forms of energy $#ther forms of energy $

    lightlight

    electricalelectrical

    kinetic and potentialkinetic and potential

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    %

    Ener!y " ChemistryEner!y " Chemistry

    &"rning pean"ts s"pply s"fficient energypean"ts s"pply s"fficient energyto oil a c"p of water.to oil a c"p of water. &"rning s"gar&"rning s"gar

    's"gar reacts with's"gar reacts with

    ()l#()l#%%* a strong* a strongo+idi,ing agent-o+idi,ing agent-

    http://xbeams.chem.yale.edu/~batista/113/movies/06z01vd1.mov
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    Ener!y " ChemistryEner!y " Chemistry

    These reactions areThese reactions are /R#0)T A3#RE0/R#0)T A3#RE0

    They proceed almost completely fromThey proceed almost completely from

    reactants to prod"cts* perhaps withreactants to prod"cts* perhaps withsome o"tside assistance.some o"tside assistance.

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    4

    Ener!y " ChemistryEner!y " Chemistry

    2 H2 H22'g- 5 #'g- 5 #22'g- 667'g- 6672 H2 H22#'g- 5 heat and light#'g- 5 heat and light

    This can e set "p to pro8ideThis can e set "p to pro8ide

    E9E)TR:) ENERGYE9E)TR:) ENERGYin ain a fue#fue#

    ce##ce##..#+idation;#+idation;

    2 H2 H226667 H6667 H55 5 e5 e66

    Red"ction;Red"ction;

    e e66 5 #5 #22 5 2 H5 2 H22# 6667 #H# 6667 #H66

    ))R* page

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    =

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Potential energyPotential energy energy a energy amotionlessmotionless

    body has bybody has byvirtue of itsvirtue of itsposition.position.

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    >

    /ositi8e andnegati8e particles'ions- attract oneanother.

    Two atoms canond

    As the particlesattract they ha8e a

    lower potentialenergy

    $otentia# Ener!y$otentia# Ener!yon the &tomic Sca#eon the &tomic Sca#e

    Na)l $ composed ofNa)l $ composed of

    NaNa55and )land )l66ions.ions.

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    ?

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Kinetic energyKinetic energy energy of energy ofmotionmotion

    TranslationTranslation

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    1@

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Kinetic energyKinetic energyenergy ofenergy ofmotion.motion.

    translate

    rotate

    vibratetranslate

    rotate

    vibrate

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    11

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    /E 5 (E :nternal energy 'E or -/E 5 (E :nternal energy 'E or -

    :nt. E of a chemical system:nt. E of a chemical system

    depends ondepends on n"mer of particlesn"mer of particles

    type of particlestype of particles

    temperat"retemperat"re

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    12

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    /E 5 (E :nternal energy 'E or -/E 5 (E :nternal energy 'E or -

    QuickTime and aGraphics decompressor

    are needed to see this picture.

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    1%

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    The higher the TThe higher the T

    the higher thethe higher the

    internal energyinternal energy Bo* "se changesBo* "se changes

    in T 'CT- toin T 'CT- to

    monitor changesmonitor changes

    in E 'CE-.in E 'CE-.

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    +irectiona#ity of Heat Transfer+irectiona#ity of Heat Transfer

    Heat always transfer from hotter o!ect to

    cooler one.

    E,Othermic; heat transfers from SYSTEMtoS-RRO-.+I./S.

    T'system- goes downT'system- goes down

    T's"rr- goes "pT's"rr- goes "p

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    1=

    +irectiona#ity of Heat Transfer+irectiona#ity of Heat Transfer

    Heat always transfer from hotter o!ect to

    cooler one.

    E.+Othermic; heat transfers fromS-RRO-.+I./S to theSYSTEM.

    T'system- goes "pT'system- goes "p

    T 's"rr- goes downT 's"rr- goes down

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    1>

    Ener!y " ChemistryEner!y " Chemistry

    All of thermodynamics dependsAll of thermodynamics dependson the law ofon the law of

    CO.SERV&TIO. O E.ER/YCO.SERV&TIO. O E.ER/Y00

    The total energy is "nchanged inThe total energy is "nchanged ina chemical reaction.a chemical reaction.

    :f /E of prod"cts is less than:f /E of prod"cts is less than

    reactants* the difference m"st ereactants* the difference m"st ereleased as (E.released as (E.

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    1 H(g) ---> H22O(g) + 242 kJO(g) + 242 kJ

    HH22O(g) ---> HO(g) ---> H22O(liq) + 44 kJO(liq) + 44 kJ

    -----------------------------------------------------------------------

    HH22(g) + 1/2 O(g) + 1/2 O22(g) --> H(g) --> H22O(liq) + 286 kJO(liq) + 286 kJ

    Example ofExample ofHESSS 8&WHESSS 8&W

    If a r;n0 is the sum of < or moreIf a r;n0 is the sum of < or moreothers6 the net 2H is the sum of theothers6 the net 2H is the sum of the2Hs of the other r;ns02Hs of the other r;ns0

    -SI./ E.TH&8$Y-SI./ E.TH&8$Y

    Hesss 8a3Hesss 8a3

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    Hess s 8a3Hess s 8a3" Ener!y 8e5e# +ia!rams" Ener!y 8e5e# +ia!rams

    orming H2# can occ"r in a

    single step or in a twosteps.

    CHtotalis the same no matter

    which path is followed.

    4

    Hesss 8a3Hesss 8a3

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    Hess s 8a3Hess s 8a3" Ener!y 8e5e# +ia!rams" Ener!y 8e5e# +ia!rams

    orming )#2can occ"r in asingle step or in a two steps.

    CHtotalis the same no matterwhich path is followed.

    =

    CCH l thH l th

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    This eD"ation is 8alid eca"seThis eD"ation is 8alid eca"seCH is aCH is a ST&TE -.CTIO.ST&TE -.CTIO.

    These depend only on the stateThese depend only on the state

    of the system andof the system and notnoton howon howthe system got there.the system got there.

    3* T* /* energy $ and yo"r ank3* T* /* energy $ and yo"r ankacco"ntOacco"ntO

    nlike 3* T* and /* one cannotnlike 3* T* and /* one cannotmeas"re asol"te H. )an onlymeas"re asol"te H. )an onlymeas"re CH.meas"re CH.

    CCH along one path H along one path

    CCH along another pathH along another path

    CCH along one path H along one path

    CCH along another pathH along another path

    >

    d d E h # #

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    Standard Entha#py Va#uesStandard Entha#py Va#ues

    Most H values are labeledMost H values are labeled HHooMeasured underMeasured understandard conditionsstandard conditions

    P = 1 bar = 10P = 1 bar = 1055Pa = 1 atm /1.01325Pa = 1 atm /1.01325

    Concentration = 1 mol/LConcentration = 1 mol/LT = usually 25T = usually 25ooCC

    with all species in standard stateswith all species in standard states

    e.g., C = graphite and Oe.g., C = graphite and O22= gas= gas

    HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g)

    (product is called (product is called water gaswater gas))

    42-sin! Standard Entha#py Va#ues-sin! Standard Entha#py Va#ues

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    ! py! py

    HH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g)

    From reference books we findFrom reference books we find

    HH22(g) + 1/2 O(g) + 1/2 O22(g) --> H(g) --> H22O(g) HO(g) Hff = - 242 kJ/mol = - 242 kJ/mol

    C(s) + 1/2 OC(s) + 1/2 O22(g) --> CO(g)(g) --> CO(g) HHff = - 111 kJ/mol = - 111 kJ/mol

    4%-sin! Standard Entha#py Va#ues-sin! Standard Entha#py Va#ues

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    HH22O(g) --> HO(g) --> H22(g) + 1/2 O(g) + 1/2 O22(g) H(g) H oo= +242 kJ= +242 kJ

    C(s) + 1/2 OC(s) + 1/2 O22(g) --> CO(g)(g) --> CO(g) HH oo= -111 kJ= -111 kJ

    --------------------------------------------------------------------------------

    To convert 1 mol of water to 1 mol each of HTo convert 1 mol of water to 1 mol each of H22

    and COand COrequiresrequires131 kJ of energy.131 kJ of energy.

    The water gas reaction isThe water gas reaction isENDOENDOthermic.thermic.

    HH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g) HHoonetnet= +131 kJ= +131 kJHH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g) HHoonetnet= +131 kJ= +131 kJ

    4

    - d d E h # V #- i St d d E th # V #

VI. Thermochem Dinamic

Jun 01, 2018

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  • 8/9/2019 VI. Thermochem Dinamic

    1/61

    1Chapter VI:Chapter VI:THERMOCHEMISTRYTHERMOCHEMISTRY

    ThermodynamicsThermodynamicsThe study of Heat and WorkThe study of Heat and Work

    and State unctionsand State unctions

  • 8/9/2019 VI. Thermochem Dinamic

    2/61

    2

    Ener!y " ChemistryEner!y " Chemistry

    Ener!y " ChemistryEner!y " Chemistry

    ENERGYENERGYis the capacity tois the capacity todo work or transfer heat.do work or transfer heat.

    HEATHEATis the form of energyis the form of energythat flows etween 2 o!ectsthat flows etween 2 o!ects

    eca"se of their difference ineca"se of their difference intemperat"re.temperat"re.

    #ther forms of energy $#ther forms of energy $

    lightlight

    electricalelectrical

    kinetic and potentialkinetic and potential

  • 8/9/2019 VI. Thermochem Dinamic

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    %

    Ener!y " ChemistryEner!y " Chemistry

    &"rning pean"ts s"pply s"fficient energypean"ts s"pply s"fficient energyto oil a c"p of water.to oil a c"p of water. &"rning s"gar&"rning s"gar

    's"gar reacts with's"gar reacts with

    ()l#()l#%%* a strong* a strongo+idi,ing agent-o+idi,ing agent-

    http://xbeams.chem.yale.edu/~batista/113/movies/06z01vd1.mov
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    Ener!y " ChemistryEner!y " Chemistry

    These reactions areThese reactions are /R#0)T A3#RE0/R#0)T A3#RE0

    They proceed almost completely fromThey proceed almost completely from

    reactants to prod"cts* perhaps withreactants to prod"cts* perhaps withsome o"tside assistance.some o"tside assistance.

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    4

    Ener!y " ChemistryEner!y " Chemistry

    2 H2 H22'g- 5 #'g- 5 #22'g- 667'g- 6672 H2 H22#'g- 5 heat and light#'g- 5 heat and light

    This can e set "p to pro8ideThis can e set "p to pro8ide

    E9E)TR:) ENERGYE9E)TR:) ENERGYin ain a fue#fue#

    ce##ce##..#+idation;#+idation;

    2 H2 H226667 H6667 H55 5 e5 e66

    Red"ction;Red"ction;

    e e66 5 #5 #22 5 2 H5 2 H22# 6667 #H# 6667 #H66

    ))R* page

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    =

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Potential energyPotential energy energy a energy amotionlessmotionless

    body has bybody has byvirtue of itsvirtue of itsposition.position.

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    >

    /ositi8e andnegati8e particles'ions- attract oneanother.

    Two atoms canond

    As the particlesattract they ha8e a

    lower potentialenergy

    $otentia# Ener!y$otentia# Ener!yon the &tomic Sca#eon the &tomic Sca#e

    Na)l $ composed ofNa)l $ composed of

    NaNa55and )land )l66ions.ions.

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    ?

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Kinetic energyKinetic energy energy of energy ofmotionmotion

    TranslationTranslation

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    1@

    $otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y$otentia# " %inetic Ener!y

    Kinetic energyKinetic energyenergy ofenergy ofmotion.motion.

    translate

    rotate

    vibratetranslate

    rotate

    vibrate

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    11

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    /E 5 (E :nternal energy 'E or -/E 5 (E :nternal energy 'E or -

    :nt. E of a chemical system:nt. E of a chemical system

    depends ondepends on n"mer of particlesn"mer of particles

    type of particlestype of particles

    temperat"retemperat"re

  • 8/9/2019 VI. Thermochem Dinamic

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    12

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    /E 5 (E :nternal energy 'E or -/E 5 (E :nternal energy 'E or -

    QuickTime and aGraphics decompressor

    are needed to see this picture.

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    1%

    Interna# Ener!y 'E(Interna# Ener!y 'E(

    The higher the TThe higher the T

    the higher thethe higher the

    internal energyinternal energy Bo* "se changesBo* "se changes

    in T 'CT- toin T 'CT- to

    monitor changesmonitor changes

    in E 'CE-.in E 'CE-.

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    14

    +irectiona#ity of Heat Transfer+irectiona#ity of Heat Transfer

    Heat always transfer from hotter o!ect to

    cooler one.

    E,Othermic; heat transfers from SYSTEMtoS-RRO-.+I./S.

    T'system- goes downT'system- goes down

    T's"rr- goes "pT's"rr- goes "p

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    1=

    +irectiona#ity of Heat Transfer+irectiona#ity of Heat Transfer

    Heat always transfer from hotter o!ect to

    cooler one.

    E.+Othermic; heat transfers fromS-RRO-.+I./S to theSYSTEM.

    T'system- goes "pT'system- goes "p

    T 's"rr- goes downT 's"rr- goes down

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    1>

    Ener!y " ChemistryEner!y " Chemistry

    All of thermodynamics dependsAll of thermodynamics dependson the law ofon the law of

    CO.SERV&TIO. O E.ER/YCO.SERV&TIO. O E.ER/Y00

    The total energy is "nchanged inThe total energy is "nchanged ina chemical reaction.a chemical reaction.

    :f /E of prod"cts is less than:f /E of prod"cts is less than

    reactants* the difference m"st ereactants* the difference m"st ereleased as (E.released as (E.

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    1 H(g) ---> H22O(g) + 242 kJO(g) + 242 kJ

    HH22O(g) ---> HO(g) ---> H22O(liq) + 44 kJO(liq) + 44 kJ

    -----------------------------------------------------------------------

    HH22(g) + 1/2 O(g) + 1/2 O22(g) --> H(g) --> H22O(liq) + 286 kJO(liq) + 286 kJ

    Example ofExample ofHESSS 8&WHESSS 8&W

    If a r;n0 is the sum of < or moreIf a r;n0 is the sum of < or moreothers6 the net 2H is the sum of theothers6 the net 2H is the sum of the2Hs of the other r;ns02Hs of the other r;ns0

    -SI./ E.TH&8$Y-SI./ E.TH&8$Y

    Hesss 8a3Hesss 8a3

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    Hess s 8a3Hess s 8a3" Ener!y 8e5e# +ia!rams" Ener!y 8e5e# +ia!rams

    orming H2# can occ"r in a

    single step or in a twosteps.

    CHtotalis the same no matter

    which path is followed.

    4

    Hesss 8a3Hesss 8a3

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    Hess s 8a3Hess s 8a3" Ener!y 8e5e# +ia!rams" Ener!y 8e5e# +ia!rams

    orming )#2can occ"r in asingle step or in a two steps.

    CHtotalis the same no matterwhich path is followed.

    =

    CCH l thH l th

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    This eD"ation is 8alid eca"seThis eD"ation is 8alid eca"seCH is aCH is a ST&TE -.CTIO.ST&TE -.CTIO.

    These depend only on the stateThese depend only on the state

    of the system andof the system and notnoton howon howthe system got there.the system got there.

    3* T* /* energy $ and yo"r ank3* T* /* energy $ and yo"r ankacco"ntOacco"ntO

    nlike 3* T* and /* one cannotnlike 3* T* and /* one cannotmeas"re asol"te H. )an onlymeas"re asol"te H. )an onlymeas"re CH.meas"re CH.

    CCH along one path H along one path

    CCH along another pathH along another path

    CCH along one path H along one path

    CCH along another pathH along another path

    >

    d d E h # #

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    Standard Entha#py Va#uesStandard Entha#py Va#ues

    Most H values are labeledMost H values are labeled HHooMeasured underMeasured understandard conditionsstandard conditions

    P = 1 bar = 10P = 1 bar = 1055Pa = 1 atm /1.01325Pa = 1 atm /1.01325

    Concentration = 1 mol/LConcentration = 1 mol/LT = usually 25T = usually 25ooCC

    with all species in standard stateswith all species in standard states

    e.g., C = graphite and Oe.g., C = graphite and O22= gas= gas

    HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g)

    (product is called (product is called water gaswater gas))

    42-sin! Standard Entha#py Va#ues-sin! Standard Entha#py Va#ues

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    ! py! py

    HH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g)

    From reference books we findFrom reference books we find

    HH22(g) + 1/2 O(g) + 1/2 O22(g) --> H(g) --> H22O(g) HO(g) Hff = - 242 kJ/mol = - 242 kJ/mol

    C(s) + 1/2 OC(s) + 1/2 O22(g) --> CO(g)(g) --> CO(g) HHff = - 111 kJ/mol = - 111 kJ/mol

    4%-sin! Standard Entha#py Va#ues-sin! Standard Entha#py Va#ues

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    HH22O(g) --> HO(g) --> H22(g) + 1/2 O(g) + 1/2 O22(g) H(g) H oo= +242 kJ= +242 kJ

    C(s) + 1/2 OC(s) + 1/2 O22(g) --> CO(g)(g) --> CO(g) HH oo= -111 kJ= -111 kJ

    --------------------------------------------------------------------------------

    To convert 1 mol of water to 1 mol each of HTo convert 1 mol of water to 1 mol each of H22

    and COand COrequiresrequires131 kJ of energy.131 kJ of energy.

    The water gas reaction isThe water gas reaction isENDOENDOthermic.thermic.

    HH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g) HHoonetnet= +131 kJ= +131 kJHH22O(g) + C(graphite) --> HO(g) + C(graphite) --> H22(g) + CO(g)(g) + CO(g) HHoonetnet= +131 kJ= +131 kJ

    4

    - d d E h # V #- i St d d E th # V #