KI1101-2012-KD Lec06b SpontaneousChangesEntropiAndFreeEnergy

8/10/2019 KI1101-2012-KD Lec06b SpontaneousChangesEntropiAndFreeEnergy

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Prentice-Hall 2007General Chemistry: Chapter 19Slide 1 of 44

Philip !tton

"ni#ersity of $indsor% Canada

Prentice-Hall 2007

CH&'(S)*+

Ninth

EditionG&,&*.

Principles and 'odern pplications

Petrucci Harwood Herring Madura

Chapter 19: Spontaneo!s Chan/e:&ntropy and ree &ner/y


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Contents

19-1 Spontaneity: )he 'eanin/ of Spontaneo!s Chan/e19-2 )he Concept of &ntropy

19- al!atin/ &ntropy and &ntropy Chan/es

19-4 Criteria for Spontaneo!s Chan/e:

)he Second .a of )hermodynamics

19-3 Standard ree &ner/y Chan/e% G5

19-6 ree &ner/y Chan/e and &!ili8ri!m

19-7 G5 andKeas !nctions of )emperat!re

19- Co!pled *eactions

Focus On Coupled Reactions in Biological Systems


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Spontaneo!s Process

process that occ!rs in a system left to itself ;nce started% no e/? A 2 e2;>s?

H2;>s? H2;>l?


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Spontaneo!s Process

Potential ener/y decreases

or chemical systems the internal ener/y Uis

e!i#alent to potential ener/y

Berthelot and )homsen 170s

Spontaneo!s chan/e occ!rs in the direction in hich

the enthalpy of a system decreases

'ainly tr!e 8!t there are e


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19-2 )he Concept of &ntropy

&ntropy% S

)he /reater the n!m8er

of confi/!rations of the

microscopic particles

amon/ the ener/y

le#els in a partic!lar

system% the /reater the

entropy of the system

SD 0 spontaneo!s

" E H E 0


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)he BoltFmann &!ation for &ntropy

&ntropy% S

States

)he microscopic ener/y le#els a#aila8le in a system

'icrostates% W

)he partic!lar ay in hich particles are distri8!ted

amon/st the states ,!m8er of microstates E W. )he BoltFmann constant% k

&ffecti#ely the /as constant per molec!le E *N

SE klnW


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Prentice-Hall 2007General Chemistry: Chapter 19Slide of 44

BoltFmann istri8!tion


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&ntropy Chan/e

SEqre#

T

or chan/es occ!rrin/at constant temperat!re


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19- al!atin/ &ntropy and

&ntropy Chan/es

Phase transitions

&s% 1 atm? H2;>l% 1 atm? Hf!sE 602 = at 2713 I

Sf!sEHf!s

Ttr

5E

602 = mol-1

2713 IE 22010-2 = mol-1I-1


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)ro!tons *!le

SE

H#ap

T8p7 = mol-1I-1


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*ao!lts .a

5P

E

P


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8sol!te &ntropies

)hird la of thermodynamics

)he entropy of a p!re perfect crystal at 0 I is Fero

Standard molar entropy

)a8!lated in ppendi<

SE J pS5>prod!cts? - rS5>reactants?K


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&ntropy as a !nction of )emperat!re


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Li8rational &ner/y and &ntropy


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19-4 Criteria for Spontaneo!s Chan/e:

)he Second .a of )hermodynamics

StotalE S!ni#erseE Ssystem@ Ss!rro!ndin/s

)he Second .a of )hermodynamics:

S!ni#erseE Ssystem@ Ss!rro!ndin/sD 0

ll spontaneo!s processes prod!ce an

increase in the entropy of the !ni#erse


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ree &ner/y and ree &ner/y Chan/e

Hypothetical process: only press!re-#ol!me or=% at constant TandP

qs!rro!ndin/sE -qpE -Hsys

'a=e the enthalpy chan/e re#ersi8le

lar/e s!rro!ndin/s% infinitesimal chan/e in temperat!re

"nder these conditions e can calc!late entropy


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ree &ner/y and ree &ner/y Chan/e

TS!ni#.E TSsysM HsysE M >HsysM TSsys?

M TS!ni#.E HsysM TSsys

GEHM TS

GE HM TS

!o" t#e uni$e"se%

!o" t#e system%

GsysE M TS!ni#erse


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Criteria for Spontaneo!s Chan/e

GsysN 0 >ne/ati#e?% the process is spontaneo!s

GsysE 0 >Fero?% the process is at e!ili8ri!m

GsysD 0 >positi#e?% the process is non-spontaneo!s

$illard Gi88s

19-190


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)a8le 191 Criteria for Spontaneo!s

Chan/e


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19-3 Standard ree &ner/y Chan/e% G5

)he standard free ener/y of formation% Gf5

)he chan/e in free ener/y for a reaction in hich a

s!8stance in its standard state is formed from its

elements in reference forms in their standard states

)he standard free ener/y of reaction% G5

G5 E J

p Gf5>prod!cts? -

r Gf5>reactants?K


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19-6 ree &ner/y Chan/e and &!ili8ri!m


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ree &ner/y Chan/e and &!ili8ri!m

Condensation &!ili8ri!m LaporiFation


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*elationship of G5 to G for

,on-standard Conditions

2 ,2>/? @ H2>/? 2 ,H>/?

GE H- TS G&E H&- TS&

or ideal /ases H ' H&

G E H&- TS


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*elationship Beteen S and S&

qre# E -(ERT ln )f)i

SEqre#

TER ln

)f

)i

SE SfM Si ER ln)f

)iER ln

Pi

PfE -R ln

Pf

Pi

SE S5-R lnP

P5E S5-R ln

P

1E S5 -R lnP


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,2>/? @ H2>/? 2 ,H>/?

S,HE

S,HM *lnP,H

S,2E

S,2M *lnP,2

SH2 E

SH2M *lnPH2

*SrS,HM *lnP,H? M >S,2M *lnP,2? M>SH2M *lnPH2?

*Sr


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G "nder ,on-standard Conditions

G E H&- TS *Sr


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G and the &!ili8ri!m ConstantKe

GE G&@RT ln +

GE G&@RT lnKeE 0

,- t#e "eaction is at equili"ium t#en%

G&E MRT lnKe


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Criteria for Spontaneo!s Chan/e

ery chemical reaction consists of 8oth aforard and a re#erse reaction

)he direction of spontaneo!s chan/e is the direction

in hich the free ener/y decreases


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Si/nificance of the 'a/nit!de of G


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)he )hermodynamic &!ili8ri!m

Constant: cti#ities

SE S5-R lnP

P5E S5-R ln

P

1

!o" ideal gases at /.0 a"%

SE S5-R ln

c

c5 E S5-R ln a

T#e"e-o"e1 in solution%

P)'nRT o" P'2n3)4RT1p"essu"e is an e--ecti$e concent"ation

)he effecti#e concentration in the standard

state for an ideal sol!tionis c5 E 1 '


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cti#ities

or p!re solids and li!ids:

O a E 1

or ideal /ases:

O a E P >in 8ars% 1 8ar E 097 atm?

or ideal sol!tes in a!eo!s sol!tion:

O a E c >in mol .-1?


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)he )hermodynamic &!ili8ri!m

Constant%Ke

dimensionless e!ili8ri!m constant e


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19-7 G&andKeas !nctions

of )emperat!re

G& ' H&M TS& G&E MRT lnKe

lnKeE M G&RTE M H&

RTTS&RT

@

lnKeEM H&

RT

S&

R@


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Lant Hoff &!ation

(f e e#al!ate this e!ation for a chan/e in temperat!re:

ln '6H&

RT7

S&

R

56H&

RT/

*S&

R

56

EMH&

R

1

T2

1

T1

M

Ke1

Ke2

ln

Ke1

Ke2


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)emperat!re ependence ofKe

lnKeE-H&

RT

S&

R@

slopeE

-H&

R

-H& ' Rslope

' -143 mol-1I-122104I

E -1102= mol-1

ss!me H& and S&do not #ary si/nificantly ith temperat!re


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19- Co!pled *eactions

(n order to dri#e a non-spontaneo!s reactions e

chan/ed the conditions >ie temperat!re or

electrolysis?

nother method is to co!ple to reactions ;ne ith a positi#e Gand one ith a ne/ati#e G

;#erall spontaneo!s process


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Smeltin/ Copper ;re

C!2;>s? A 2 C!>s? @ Q ;2>/?G&67IE @123 =

C!2;>s? @ C>s? A 2 C!>s? @ C;>/?

Spontaneous "eaction8

C!2;>s? A 2 C!>s? @ Q ;2>/?Non6spontaneous "eaction% @123 =

C>s? @ Q ;2>/? A C;>/?Spontaneous "eaction% -173 =

-30 =


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Focus OnCo!pled *eactions in

Biolo/ical Systems


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Prentice-Hall 2007General Chemistry: Chapter 19

Slide 41 of 44

)he Biolo/ical Standard State

P-@ HP;42-@ H@ A )P4-@ H2;

G&E -92 = mol-1

G ' G& 5 RT ln

a)PaH2;

a9PaPiaH;@

But JH;@K' 10-7 ' not 10 '

G ' -92 = mol-1@ 416 = mol-1

E @24 = mol-1E G&:

P to )P is not spontaneo!s and 8iolo/ical systems !se /l!cose


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Slide 42 of 44

oc!s ;n Co!pled *eactions in

Biolo/ical Systems

Gl!cose A 2 lactate @ 2 H@ -21 =

2 P-@ 2 HP;42-@ 2 H@ A 2 )P4-@ 2 H2; @64 =

2 P-@ 2 HP;42-@ /l!cose A 2 )P4-@ 2 H2; @ 2 lactate -13 =


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Slide 4 of 44

&nd of Chapter R!estions

d

nser

$or= a pro8lem from 8oth ends to find the =ey

lo/

d

e

f

a

8

c

e


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Prentice-Hall 2007Slide 44 of 44

&nd of Chapter R!estions

d

nser

$or= a pro8lem from 8oth ends to find the =ey

lo/

d

e

f

a

8

c

e

KI1101-2012-KD Lec06b SpontaneousChangesEntropiAndFreeEnergy

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