ib chemistry on entropy and laws of thermodynamics

http://lawrencekok.blogspot.com

Prepared by Lawrence Kok

Tutorial on Entropy and 1st, 2nd and 3rd Law of Thermodynamics .

http://lawrencekok.blogspot.com/

E = sum kinetic energy/motion of molecule, and potential energy represented by chemical bond bet atom

∆E = q + w

∆E = Change internal energy

q = heat transfer

w = work done by/on system

Thermodynamics Study of work, heat and energy on a system

∆E universe = ∆E sys + ∆E surrounding = 0

1st Law Thermodynamics

Entropy - Measure of disorder↓

∆S uni = ∆S sys + ∆S surr > 0 (irreversible rxn)↓

All spontaneous rxn produce increase in entropy of universe

2nd Law Thermodynamics

∆S uni = ∆S sys + ∆S surr

Isolated system - Entropy change of universe always increase

Click here thermodynamics entropyEntropy

Measure molecular disorder/randomness

↓More disorder - More dispersion of matter/energy

↓More random - Rxn toward right- Entropy Increases ↑

Direction to right- Spontaneous to right →

2nd Law Thermodynamics

Embrace the chaos

Over time - Entropy increase ↑

Direction to left ← Never happen !

Click here thermodynamics

Energy cannot be created or destroyed

> 0

https://www.youtube.com/watch?v=MALZTPsHSoo

https://www.youtube.com/watch?v=GOrWy_yNBvY

∆S = Entropy change

Entropy

Dispersal/Distribution

Matter Energy

Matter more disperse ↑

Entropy increases ↑

solid liquid gas

spontaneous - entropy ↑

Over time - Entropy increase ↑

Phase change - sol → liq → gas

↓ Entropy increase ↑ Every energy transfer - increase entropy universe

Entropy universe can only go up - never go down Entropy increase - many ways energy spread out

Dispersion energy as heat - increase entropy

Stoichiometry- more gas/liq in product

↓Entropy increase ↑

TQS

Heat added ↑

Phase change

Stoichiometry

Embrace the chaos

N2O4(g) → 2NO2(g)

1 2

2H2O(l) → 2H2 (g) + O2 (g)

1 23

3

More gas in product - Entropy ↑

Heat added ↑

Entropy

Measure molecular disorder/randomness↓

More disorder - More dispersion of matter/energy↓

More randon - Rxn towards right- Entropy Increases ↑

Liq more disorder than solidGas more disorder than liq

kinetic energy distributed over wide range

Q = heat

transferT = Temp/K

Distribution matter in space Distribution energy bet particles

Direction to left ← Never happen !Direction to right- Spontaneous to right →

Statistical

Entropy

Entropy

Measure molecular disorder/randomness↓

More disorder - More dispersion of matter/energy↓

More random - Entropy Increases ↑

1st Law Thermodynamics - Doesn't help explain direction of rxn

∆S uni > 0 (+ve) → More disorder - spontaneous∆S uni < 0 (-ve) → More order - non spontaneous

Change sol → liq → gas - Higher entropyGreater number particles in product - Higher entropyMore complex molecule - More atoms bonded - Higher

entropyHigher temp - Vibrate faster - More random - Higher entropy

Why gas mixes and not unmix?

Why heat flow from hot to cold?

Entropy

Notes on Entropy

1st Law Thermodynamics 2nd Law Thermodynamics

Energy cannot be created or destroyedTransfer from one form to another


Isolated system ↓

∆S uni always increase

∆E = q + w

Method to calculate entropy

Number microstates

Thermodynamic

Entropy

Heat + Temp involved

Gas mixesSolution diffuse Heat flow hot →cold

X X X

∆E = internal energy

q = heat transfer

w = work done ∆S = Entropy universe

∆S = Entropy system

∆S = Entropy surrounding


Law Thermodynamics

1 2

∆S = Entropy uni

WkS ln

∆S = Entropy change

k = boltzmann constant

W = Microstate

Click here statistical entropy

Click here thermodynamics entropy

Why solution diffuse and not undiffuse?

Unit - J mol -1

K-1

surrsysuni SSS

∆S = Entropy sys and surr

https://www.youtube.com/watch?v=bE7Z6Zkst1I&list=PLX2gX-ftPVXUeVHmfT2BkhcEibTeReWKg

https://www.youtube.com/watch?v=bE7Z6Zkst1I&list=PLX2gX-ftPVXUeVHmfT2BkhcEibTeReWKg

1st Law Thermodynamics - Doesn't help explain direction of rxn

∆S uni > 0 (+ve) → More disorder - spontaneous∆S uni < 0 (-ve) → More order - non spontaneous

Change sol → liq → gas - Higher entropyGreater number particles in product - Higher entropyMore complex molecule - More atoms bonded - Higher

entropyHigher temp - Vibrate faster - More random - Higher entropyMeasure molecular disorder/randomness

↓More disorder - More dispersion of matter/energy

↓More random - Entropy Increases ↑

Isolated system ↓

∆S uni always increase

Entropy



Notes on Entropy




∆E = q + w


X X X


q = heat transfer

w = work done ∆S = Entropy universe




Law Thermodynamics

3rd Law Thermodynamics

Unit - J mol -1

K-1

Standard Molar Entropy, S0

Entropy perfectly crystal at 0K = 0Std molar entropy, S0

↓S0 when substance heated from 0K to

298K

Std state - 1 atm / 1M sol

Temp = 298K

Std Molar Entropy/S0

S0 at 298 /JK-1 mol-1

Fe (s) + 27

H2O (s) + 48

Na (s) + 52

H2O (l) + 69

CH3OH (l) + 127

H2 (g) + 130

H2O (g) + 188

CO2 (g) + 218

Solid - Order↓

Entropy Lowest

Liq - Less order↓

Entropy Higher

Gas - Disorder↓

Entropy Highest

Entropy highest


Entropy

Why gas mix and not unmix?




X X X

Unit - J mol -1

K-1


Entropy perfectly crystal at 0K = 0↓

S0 when substance heated from 0K to 298K


Temp = 298K


S0 at 298 /JK-1 mol-1

Fe (s) + 27

H2O (s) + 48

Na (s) + 52

H2O (l) + 69

CH3OH (l) + 127

H2 (g) + 130

H2O (g) + 188

CO2 (g) + 218

Solid - Order↓

Entropy Lowest

Liq - Less order↓

Entropy Higher

Gas - Disorder↓

Entropy Highest

Entropy highest

Entropy


Depend on

Temp increase ↑ - Entropy increase ↑

Physical/phase state

Dissolving solid Molecular mass

Click here thermodynamics entropy Ba(OH)2

Temp

Temp/K 273 295 298

S0 for H2 + 31 + 32 + 33.2

Sol → Liq → Gas - Entropy increase ↑

State solid liquid gas

S0 for H2O + 48 + 69 + 188

entropy increase ↑ entropy increase ↑

Depend on

Substance NaCI NH4NO3

S0 for solid + 72 + 151

S0 for aq + 115 + 260

More motion - entropy increase ↑ Higher mass - entropy increase ↑

Substance HF HCI HBr

Molar mass 20 36 81

S0 + 173 + 186 + 198

S0 = 0 at 0KAll sub > 0K, have +ve S0

https://www.youtube.com/watch?v=ZsY4WcQOrfk

Entropy perfectly crystal at 0K = 0↓


Entropy

Why gas mix and not unmix?




X X X

Unit - J mol -1

K-1



Temp = 298K


S0 at 298 /JK-1 mol-1

H2O (s) + 48

Na (s) + 52

H2O (l) + 69

CH3OH (l) + 127

H2O (g) + 188

CO2 (g) + 218

Solid - Order↓

Entropy Lowest

Liq - Less order↓

Entropy Higher

Gas - Disorder↓

Entropy Highest

Entropy highest

Entropy


Depend on

Temp increase ↑ - Entropy increase ↑

Physical/phase state

Dissolving solid Molecular mass

Temp

Temp/K 273 295 298

S0 for H2 + 31 + 32 + 33.2

Sol → Liq → Gas - Entropy increase ↑

State solid liquid gas

S0 for H2O + 48 + 69 + 188

entropy increase ↑ entropy increase ↑

Depend on

More motion - entropy increase ↑

Click here entropy notes

Click here entropy, enthalpy free energy data

Click here entropy CRC data booklet

Higher mass - entropy increase ↑

S0 = 0 at 0KAll sub > 0K, have +ve S0

Substance NaCI NH4NO3

S0 for solid + 72 + 151

S0 for aq + 115 + 260

Substance HF HCI HBr

Molar mass 20 36 81

S0 + 173 + 186 + 198

Entropy


Why conc solution diffuse and not undiffuse?


Entropy

Thermodynamic Entropy


X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Less number gas↓

Entropy surr ↑ increase - Heat release increase ↑ motion surr particles

↓Heat release by sys to surr increase ↑ entropy surr

↓∆S surr > ∆S sys (More +ve)

↓∆S uni = ∆S sys + ∆S surr

↓∆S uni > 0 - Combustion at 298K - Spontaneous

surrsysuni SSS

)tan()( treacprosys SSS

C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(l) ∆H = -2220 kJ at 298K

C3H8(g) + 5 O2 (g) → 3 CO2(g) + 4 H2O(l) S0 +270 +205 x 5 +213 x 3 +70 x 4 1295 919

Reactant Product

17450298

)2220000(

JKS

S

THS

surr

surr

surr

1

)tan()(

376

1295919

JKS

S

SSS

sys

sys

treacproductsys

170747450376

JKS

SSS

uni

surrsysuni

∆H = -2220 kJ = -2220000J

surrsysuni SSS S /JK-1

Assume Q = H at constant pressure

+ve

-ve

spontaneous

∆Ssys = - 376

∆Ssurr = +7450

=+

∆Suni = + 7074

∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous

Is Combustion at 298K spontaneous?

Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Less number gas↓

Entropy surr ↑ increase - Heat released increase ↑ motion surr particles




↓∆S uni > 0 - Combustion at 298K - Spontaneous

surrsysuni SSS


CH4(g) + 2O2 (g) → CO2(g) + 2H2O(g) ∆H = - 890 kJ at 298K

CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g) S0 + 186 +205 x 2 +213 + 188 x 2 + 596 + 589

Reactant Product

12986298

)890000(

JKS

S

THS

surr

surr

surr

1

)tan()(

7

596589

JKS

S

SSS

sys

sys

treacproductsys

1297929867

JKS

SSS

uni

surrsysuni

∆H = - 890 kJ = - 890 000J


+ve

-ve

spontaneous

∆Ssys = - 7

∆Ssurr = + 2986

=+

∆Suni = + 2979




Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Liquid form↓





↓∆S uni > 0 - Condensation at 298K - Spontaneous

surrsysuni SSS


H2O (g) → H2O(l) ∆H = - 44.1 kJ at 298K

H2O (g) → H2O(l) S0 + 188 + 70 + 188 + 70

Reactant Product

1148298

)44100(

JKS

S

THS

surr

surr

surr

1

)tan()(

118

18870

JKS

S

SSS

sys

sys

treacproductsys

130148118

JKS

SSS

uni

surrsysuni

∆H = -44.1 kJ = - 44 100J


+ve

-ve

spontaneous

∆Ssys = - 118

∆Ssurr = + 148

=+

∆Suni = + 30


Condensation steam at 298K (25C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↑ increase - More disorder - More gas atoms form

↓Entropy surr ↓ decrease - Heat absorb decrease ↓ motion

surr particles↓

Heat absorb by sys from surr decrease ↓ entropy surr↓

∆S surr < ∆S sys (More -ve)↓

∆S uni = ∆S sys + ∆S surr↓

∆S uni < 0 - Atomization at 298K - Non Spontaneous

surrsysuni SSS


H2(g) → 2 H(g) ∆H = + 436 kJ at 298K

H2 (g) → 2 H(g) S0 + 130 + 115 x 2 + 130 + 230

Reactant Product

11463298

)436000(

JKS

S

THS

surr

surr

surr

1

)tan()(

100

130230

JKS

S

SSS

sys

sys

treacproductsys

113631463100

JKS

SSS

uni

surrsysuni

∆H = + 436 kJ = + 436 000J


+ve

-ve

non - spontaneous

∆Ssys = +100

∆Ssurr = - 1463

=+

∆Suni = - 1363


Is Atomization of H2 at 298K spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Solid form↓



↓∆S sys > ∆S surr (More -ve)


↓∆S uni < 0 - Freezing at 298K - Non Spontaneous

surrsysuni SSS


H2O (l) → H2O(s) ∆H = - 6 kJ at 298K

H2O (l) → H2O(s) S0 + 70 + 48 + 70 + 48

Reactant Product

120298

)6000(

JKS

S

THS

surr

surr

surr

1

)tan()(

22

7048

JKS

S

SSS

sys

sys

treacproductsys

122022

JKS

SSS

uni

surrsysuni

∆H = -6 kJ = - 6000J


+ve

-ve

non - spontaneous

∆Ssys = - 22

∆Ssurr = + 20

=+∆Suni= - 2


Is Freezing water to ice at 298K (25C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Solid form↓





↓∆S uni > 0 - Freezing at 263K (-10C) - Spontaneous

surrsysuni SSS


H2O (l) → H2O(s) ∆H = - 6 kJ at 263K

H2O (l) → H2O(s) S0 + 70 + 48 + 70 + 48

Reactant Product

18.22263

)6000(

JKS

S

THS

surr

surr

surr

1

)tan()(

22

7048

JKS

S

SSS

sys

sys

treacproductsys

18.08.2222

JKS

SSS

uni

surrsysuni

∆H = -6 kJ = - 6000J


+ve

-ve

spontaneous

∆Ssys = - 22

∆Ssurr = + 22.8

=+∆Suni= + 0.8


Is Freezing water to ice at 263K (-10C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↑ increase - More disorder - Gas form↓

Entropy surr ↓ decrease - Heat absorb decrease ↓ motion surr particles

↓Heat absorb by sys from surr decrease ↓ entropy surr

↓∆S surr < ∆S sys (More -ve)


↓∆S uni < 0 - Decomposition at 298K - Non Spontaneous

surrsysuni SSS


CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 298K

CaCO3 (s) → CaO (s) + CO2(g) S0 + 93 + 40 + 213 + 93 + 253

Reactant Product

1597298

)178000(

JKS

S

THS

surr

surr

surr

1

)tan()(

160

93253

JKS

S

SSS

sys

sys

treacproductsys

1437597160

JKS

SSS

uni

surrsysuni

∆H = + 178 kJ =+ 178 000J


+ve

-ve non - spontaneous

∆Ssys = + 160

∆Ssurr = - 597

=+

∆Suni= - 437


Decomposition CaCO3 at 298K (25C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↑ increase - More disorder - Gas form↓

Entropy surr ↓ decrease - Heat aborb decrease ↓ motion surr particles

↓Heat absorb by sys from surr decrease ↓ entropy surr

↓∆S sys > ∆S surr (More +ve)


↓∆S uni > 0 - Decomposition at 1500K - Spontaneous

surrsysuni SSS


CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 1500K

CaCO3 (s) → CaO (s) + CO2(g) S0 + 93 + 40 + 213 + 93 + 253

Reactant Product

11181500

)178000(

JKS

S

THS

surr

surr

surr

1

)tan()(

160

93253

JKS

S

SSS

sys

sys

treacproductsys

142118160

JKS

SSS

uni

surrsysuni

∆H = + 178 kJ =+ 178 000J


+ve

-ve

spontaneous

∆Ssys = + 160

∆Ssurr = - 118

=+∆Suni = + 42


Decomposition CaCO3 at 1500K (1227C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Less gas form↓





↓∆S uni > 0 - Oxidation at 298K - Spontaneous

surrsysuni SSS


2NO(g) + O2(g) → 2NO2(g) ∆H = - 114 kJ at 298K

2 NO(g) + O2 (g) → 2NO2(g) S0 + 210 x 2 + 102 + 240 x 2 + 522 + 480

Reactant Product

1382298

)114000(

JKS

S

THS

surr

surr

surr

1

)tan()(

42

522480

JKS

S

SSS

sys

sys

treacproductsys

133938242

JKS

SSS

uni

surrsysuni

∆H = - 114 kJ = - 114 000J


+ve

-ve

spontaneous

∆Ssys = - 42

∆Ssurr = + 382

=+∆Suni = + 339


Is Oxidation of NO at 298K (25C) spontaneous?


Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order - Less gas form↓





↓∆S uni > 0 - NH3 production at 298K - Spontaneous

surrsysuni SSS


N2(g) + 3H2(g) → 2NH3(g) ∆H = - 92 kJ at 298K

N2(g) + 3H2 (g) → 2NH3(g) S0 + 192 + 131 x 3 + 192 x 2 + 585 + 384

Reactant Product

1308298

)92000(

JKS

S

THS

surr

surr

surr

1

)tan()(

201

585384

JKS

S

SSS

sys

sys

treacproductsys

1107308201

JKS

SSS

uni

surrsysuni

∆H = - 92 kJ = - 92 000J


+ve

-ve

spontaneous

∆Ssys = - 201

∆Ssurr = + 308

=+∆Suni = + 107


Is Haber, NH3 production 298K (25C) spontaneous?


NH3

Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order ↓





↓∆S uni > 0 - AI production at 298K - Spontaneous

surrsysuni SSS


Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) ∆H = - 851 kJ at 298K

+ 143 + 105Reactant Product

12855298

)851000(

JKS

S

THS

surr

surr

surr

1

)tan()(

38

143105

JKS

S

SSS

sys

sys

treacproductsys

12817285538

JKS

SSS

uni

surrsysuni

∆H = - 851 kJ = - 851 000J


+ve

-ve

spontaneous

∆Ssys = - 38

∆Ssurr = + 2855

=+

∆Suni = + 2817


Is Thermite, AI production 298K (25C) spontaneous?


Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) S0 + 87 + 28 x 2 + 27 x 2 + 51

Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↓ decrease - More order ↓

Entropy surr ↑ increase - Heat release increase motion surr particles




↓∆S uni > 0 - Decomposition KCIO3 at 298K - Spontaneous

surrsysuni SSS


4KCIO3(s) → 3KCIO4(s) + KCI(s) ∆H = - 144 kJ at 298K


1483298

)144000(

JKS

S

THS

surr

surr

surr

1

)tan()(

37

572535

JKS

S

SSS

sys

sys

treacproductsys

144648337

JKS

SSS

uni

surrsysuni

∆H = - 144 kJ = - 144 000J


+ve

-ve

spontaneous

∆Ssys = - 37

∆Ssurr = + 483

=+∆Suni = + 446


Is decomposition KCIO3

298K (25C) spontaneous?


∆S/∆H constant over range of temp

4KCIO3(s) → 3KCIO4(s) + KCI(s) S0 + 143 x 4 + 151 x 3 + 82

Entropy




Entropy



X X X

1Quatitatively

TH

TQSsurr

Quatitatively

Entropy sys ↑ increase - More disorder ↓

Entropy surr ↑ increase - Heat release increase ↑ motion particles


↓∆S surr + ∆S sys > 0 (More +ve)


↓∆S uni > 0 Combustion sugar at 298K - Spontaneous

surrsysuni SSS


C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ at 298K


19430298

)2810000(

JKS

S

THS

surr

surr

surr

1

)tan()(

877

8211698

JKS

S

SSS

sys

sys

treacproductsys

1103079430877

JKS

SSS

uni

surrsysuni

∆H = - 2810 kJ = - 2810 000J


+ve

-ve spontaneous∆Ssys = + 877

∆Ssurr = + 9430

=+

∆Suni = + 10307


Is combustion sugar 298K (25C) spontaneous?


∆S/∆H constant over range of temp

C6H12O6 (s) + 6O2(g) → 6CO2(g) + 6H2O(l) S0 + 209 +102 x 6 + 213 x 6 + 70 x 6


↓∆S uni > 0


↓∆S uni > 0

q = heat transfer

Isolated system ∆S uni always

increase




∆E = q + w


w = work done

∆S = Entropy universe




Law Thermodynamics


Unit - J mol -1 K-1





Temp = 298K

spontaneous+ve

-ve

=

S /JK-1

Exothermic - Heat released

∆Ssys = + ve

∆Ssurr = + ve

∆Suni = + ve

+

∆S sys + ve , ∆S surr +ve↓

Suni > 0(Rxn always

spontaneous)


+ve

-ve∆Ssys = - ve

+

∆Ssurr = + ve

∆Suni = + ve

= spontaneous

∆S sys - ve and ∆S surr + ve

↓Suni > 0

(Rxn spontaneous)

Endothermic - Heat absorb

S /JK-1 S /JK-1

∆Ssys = + ve

+

∆Ssurr = - ve

=

∆Suni = + ve

∆S sys + ve and ∆S surr - ve

↓Suni > 0

(Rxn spontaneous)

spontaneous


↓∆S uni > 0

C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ

Spontaneous / non spontaneous∆Hsys and ∆Suni

2NO(g) + O2(g) → 2NO2(g) ∆H = - 114 kJ

CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ

∆H = -ve ∆H = -ve ∆H = +ve


↓∆S uni< 0


↓∆S uni < 0


↓∆S uni < 0

q = heat transfer

Isolated system ∆S uni always

increase




∆E = q + w


w = work done

∆S = Entropy universe




Law Thermodynamics


Unit - J mol -1 K-1





Temp = 298K

Nonspontaneous

+ve

-ve=

S /JK-1


∆Ssys = + ve

∆Ssurr = - ve∆Suni = - ve

+

∆S sys + ve , ∆S surr - ve↓

Suni < 0(Rxn always Non

spontaneous)


+ve

-ve

∆Ssys = - ve

+

∆Ssurr = + ve

∆Suni = - ve=

∆S sys - ve, ∆S surr + ve↓

Suni < 0(Rxn Non

spontaneous)


S /JK-1 S /JK-1

∆Ssys = + ve

+

∆Ssurr = - ve

=

∆Suni = - ve

∆S sys + ve and ∆S surr - ve

↓Suni < 0

(Rxn Non spontaneous)

Spontaneous / non spontaneous∆Hsys and ∆Suni

∆H = + ve ∆H = + ve ∆H = - ve

CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ

H2O (l) → H2O(s) ∆H = - 6 kJ

Nonspontaneous

H2(g) → 2 H(g) ∆H = + 436 kJ

Nonspontaneous

Entropy




Predict entropy change - quatitatively


X X X

Reactant Product

CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)

CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(l) ∆Hf

0 - 74 0 - 393 - 286 x 2 S0 + 186 +205 x 2 + 213 + 70 x 2

∆Hsysθ = ∑∆Hf

θ(pro) - ∑∆Hf

θ(react)∆Ssys

θ = ∑Sfθ(pro) - ∑Sf

θ(react)

1

)tan()(

243

596353

JKS

S

SSS

sys

sys

treacproductsys

12990298

)891000(

JKS

S

THS

surr

surr

surr

kJH sys 891)74(965

surrsysuni SSS

127472990243

JKS

SSS

uni

surrsysuni


Unit for ∆S - JK-1 Unit for ∆H - kJ


∆S uni > 0 - Combustion at 298K - Spontaneous

C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(l)

C3H8(g) + 5 O2 (g) → 3 CO2(g) + 4 H2O(l) ∆Hf

0 - 104 0 - 393 x 3 - 286 x 4S0 +270 +205 x 5 +213 x 3 + 70 x 4

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react) ∆Hsys

θ = ∑∆Hfθ(pro) - ∑∆Hf

θ(react)

1

)tan()(

376

1295919

JKS

S

SSS

sys

sys

treacproductsys kJH sys 2219)104(2323

17446298

)2219000(

JKS

S

THS

surr

surr

surr

surrsysuni SSS

170707446376

JKS

SSS

uni

surrsysuni


∆S uni > 0 - Combustion at 298K - Spontaneous

1 2

Entropy






X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)∆Ssys


θ(react)

1

)tan()(

118

18870

JKS

S

SSS

sys

sys

treacproductsys

1148298

)44000(

JKS

S

THS

surr

surr

surr

kJH sys 44)242(286

surrsysuni SSS

130148118

JKS

SSS

uni

surrsysuni

Is Condensation/Freezing at 298K spontaneous?


∆S uni > 0 - Condensation at 298K - Spontaneous

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react) ∆Hsys


θ(react)

1

)tan()(

22

7048

JKS

S

SSS

sys

sys


120298

)6000(

JKS

S

THS

surr

surr

surr

surrsysuni SSS

122022

JKS

SSS

uni

surrsysuni


∆S uni < 0 -Freezing at 298K - Non Spontaneous

3 4 H2O (g) → H2O(l)

H2O (l) → H2O(s)

H2O (g) → H2O(l) ∆Hf

0 - 242 - 286S0 + 188 + 70

H2O (l) → H2O(s) ∆Hf

0 - 286 - 292S0 + 70 + 48

Entropy






X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)∆Ssys


θ(react)

1308298

)92000(

JKS

S

THS

surr

surr

surr

kJH sys 92)0(92

surrsysuni SSS

1107308201

JKS

SSS

uni

surrsysuni

Are these rxn at 298K spontaneous?


∆S uni > 0 - NH3 production at 298K - Spontaneous

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react) ∆Hsys


θ(react)

kJH sys 168)1564(1732

1563298

)168000(

JKS

S

THS

surr

surr

surr

surrsysuni SSS

152656337

JKS

SSS

uni

surrsysuni


∆S uni > 0 - Decomposition at 298K - Spontaneous

5 6N2(g) + 3H2(g) → 2NH3(g)

N2(g) + 3H2 (g) → 2NH3(g) ∆Hf

0 0 0 - 46 x 2S0 + 192 + 131 x 3 + 192 x 2

1

)tan()(

201

585384

JKS

S

SSS

sys

sys

treacproductsys

4KCIO3(s) → 3KCIO4(s) + KCI(s)

4KCIO3(s) → 3KCIO4(s) + KCI(s) ∆Hf

0 - 391 x 4 - 432 x 3 - 436S0 + 143 x 4 + 151 x 3 + 82

1

)tan()(

37

572535

JKS

S

SSS

sys

sys

treacproductsys

11181500

)178000(

JKS

S

THS

surr

surr

surr

Entropy






X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)∆Ssys


θ(react)

kJH sys 178)1206(1028

surrsysuni SSS

1437597160

JKS

SSS

uni

surrsysuni


∆S uni < 0 - Decomposition at 298K - Non Spontaneous

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react) ∆Hsys


θ(react)

surrsysuni SSS

142118160

JKS

SSS

uni

surrsysuni


∆S uni > 0 - Decomposition at 1500K - Spontaneous

7 8CaCO3 (s) → CaO(s) + CO2(g)

CaCO3 (s) → CaO (s) + CO2(g) ∆Hf

0 - 1206 - 635 - 393S0 + 93 + 40 + 213

1

)tan()(

160

93253

JKS

S

SSS

sys

sys

treacproductsys

Decomposition at 298K Decomposition at 1500K

CaCO3 (s) → CaO(s) + CO2(g)

CaCO3 (s) → CaO (s) + CO2(g) ∆Hf

0 - 1206 - 635 - 393S0 + 93 + 40 + 213

1

)tan()(

160

93253

JKS

S

SSS

sys

sys


Rxn Temp dependentSpontaneous at High ↑Temp

1500K (1227C)298K (25C)

Decomposition limestone CaCO3 spontaneous?

1597298

)178000(

JKS

S

THS

surr

surr

surr

Entropy






X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)∆Ssys


θ(react)

1

)tan()(

22

7048

JKS

S

SSS

sys

sys


surrsysuni SSS

122022

JKS

SSS

uni

surrsysuni

Is Freezing spontaneous?

Unit for ∆S - JK-1 Unit for ∆H - kJ


∆S uni < 0 - Freezing at 298K - Non Spontaneous

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react) ∆Hsys


θ(react)

1

)tan()(

22

7048

JKS

S

SSS

sys

sys


18.22263

)6000(

JKS

S

THS

surr

surr

surr

surrsysuni SSS

18.08.2222

JKS

SSS

uni

surrsysuni


∆S uni > 0 -Freezing at 263K - Spontaneous

9 10 H2O (l) → H2O(s)

H2O (l) → H2O(s)


0 - 286 - 292S0 + 70 + 48


0 - 286 - 292S0 + 70 + 48

Freezing at 298K (25C) Freezing at 263K (-10C)

Rxn Temp dependentSpontaneous at Low ↓ temp

120298

)6000(

JKS

S

THS

surr

surr

surr

263K (-10C)298K (25C)

N2O4 (g) → 2NO2(g)

Reactant Product

Entropy

Ice (s) Water (l)

Entropy






X X X

Qualitatively

Solid → Liquid

NaCI(s) → Na+(aq) + CI

-(aq)

N2O4 (g) → 2NO2(g)

Reactant ProductS θ Less More

More microstates (More dispersion/random/freedom of motion)

Solid → liq → gas

Higher ↑ entropy

Greater number particles in product

More liq/gas in product

Dispersion Energ

y Microstat

e

More dispersion of energy(Electronic, translational, rotational, vibrational, thermal)

Higher entropy ∆S > 0 (+ve) - Spontaneous

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

∆Srysθ = More - Less

= +ve > 0

S θ Less More

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

∆Ssysθ = More - Less

= +ve > 0

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)


= +ve > 0

NaCI(s) → Na+(aq) +

CI -(aq)

S θ Less MoreReactant Product

QualitativelyUnit - J mol -1

K-1

Reactant Product

Entropy

Liq N2(l) Gas N2 (g)

Entropy






X X X

Qualitatively

Liquid → Gas

Reactant ProductS θ Less More

More microstates (More dispersion/random/freedom of motion)

Solid → liq → gas

Higher entropy

Greater number particles in product

More liq/gas in product

Dispersion Energ

y Microstat

e

More dispersion of energy(Electronic, translational, rotational, vibrational, thermal)

Higher entropy ∆S > 0 (+ve) - Spontaneous

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)


= +ve > 0

S θ Less More

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)


= +ve > 0

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)


= +ve > 0

NH4NO3(s) → NH4+

(aq) + NO3 -

(aq)

S θ Less More Reactant Product

Qualitatively

NH4NO3 (s) → NH4 +(aq) + NO3

- (aq) Ba(OH)2 .8H2O(s) + 2NH4NO3 (s) → Ba2+

(aq) + 2NO3-(aq) + 2NH3 (g) +

10H2O(aq)

Ba(OH)2 .8H2O(s) + 2NH4NO3 (s) → Ba2+(aq) + 2NO3

- (aq) + 2NH3

(g) +10H2O(aq)

Unit - J mol -1

K-1

+

Entropy decrease ↓

Entropy




Predict entropy change - qualitatively


X X X

NH4NO3 (s) → NH4 +(aq) + NO3

- (aq)

C3H8(g) + 5O2 (g) → 3CO2(g) + 4H2O(g)

2H2(g) + O2 (g) → 2H2O(l)

2Cu(s) + O2 (g) → 2CuO(s)

Br2(l) → Br2(g)

Ag+(aq) + Br-

(aq) → AgBr(s)

H2(g) + CI2 (g) → 2HCI(g)

Cu2+(aq) + Zn(s) → Cu(s) +

Zn2+(aq)

CaCO3 (s) → CaO(s) + CO2

(g)

1

Entropy decrease ↓

Entropy decrease ↓ Entropy increase ↑

Entropy increase ↑Entropy increase ↑

Entropy increase ↑

Little change

Little change

2 3

4

Reactant Productaq - more disorder solid - more order S higher ↑ S - Lower ↓

Reactant Product

g - more disorder solid - more order S higher ↑ S - Lower ↓

Reactant Product

Both sides equal number mol gas

Reactant Productg - more disorder liq - more order S higher ↑ S - Lower ↓

Reactant Productliq- more order g - more disorder S Lower ↓ S - Higher↑

Reactant Productless g- more order more g - more disorder S Lower ↓ S - Higher↑

Reactant Product

Both sides equal number mol solid

Reactant Productsolid- more order aq - more disorder S Lower ↓ S - Higher↑

Reactant Productsolid- more order g - more disorder S Lower ↓ S - Higher↑

5 6

7 8 9

ib chemistry on entropy and laws of thermodynamics

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