IB Chemistry on Entropy and Laws of Thermodynamics

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 entropy Entropy

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

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 ↓


T

QS

Heat added ↑ Phase change Stoichiometry

Embrace the chaos

N2O4(g) → 2NO2(g)

1 2

2H2O(l) → 2H2 (g) + O2 (g)

1 2 3

3

More gas in product - Entropy ↑

Heat added ↑

Entropy



More randon - Rxn towards right- Entropy Increases ↑

Liq more disorder than solid Gas more disorder than liq

kinetic energy distributed

over wide range

Q = heat transfer

T = Temp/K

Distribution matter in space Distribution energy bet particles

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

Statistical Entropy

Entropy



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 entropy Greater number particles in product - Higher entropy

More complex molecule - More atoms bonded - Higher entropy Higher 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 destroyed Transfer 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 mixes Solution 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=MGA2uGck3iQ&list=PLX2gX-ftPVXVhAmhi4e10J7PN6_1cvBYi&index=1


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 entropy Greater number particles in product - Higher entropy

More complex molecule - More atoms bonded - Higher entropy Higher temp - Vibrate faster - More random - Higher entropy



More random - Entropy Increases ↑

Isolated system ↓

∆S uni always increase

Entropy

Why gas mixes and not unmix? Why heat flow from hot to cold?

Notes on Entropy




∆E = q + w


X X X


q = heat transfer





Law Thermodynamics

3rd Law Thermodynamics

Unit - J mol -1 K-1

Standard Molar Entropy, S0

Entropy perfectly crystal at 0K = 0 Std 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

Why solution diffuse and not undiffuse?

Entropy

Why gas mix and not unmix? Why solution diffuse and not undiffuse? Why heat flow from hot to cold?


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


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 0K All sub > 0K, have +ve S0

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

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


Entropy perfectly crystal at 0K = 0 ↓


Entropy

Why gas mix and not unmix? Why solution diffuse and not undiffuse? Why heat flow from hot to cold?


X X X

Unit - J mol -1 K-1



Temp = 298K


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 0K All 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

http://www2.sunysuffolk.edu/sambass/index_files/ch34old/lectures/pdfs/ch19.pdf

http://www.chemistry-reference.com/Standard%20Thermodynamic%20Values.pdf

http://www.fptl.ru/biblioteka/spravo4niki/handbook-of-Chemistry-and-Physics.pdf


http://www.chemistry-reference.com/Standard%20Thermodynamic%20Values.pdf


Entropy

Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?

Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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

17450

298

)2220000(

JKS

S

T

HS

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

1 Quatitatively

T

H

T

QSsurr

Quatitatively

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

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





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

12986

298

)890000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

7

596589

JKS

S

SSS

sys

sys

treacproductsys

1297929867

JKS

SSS

uni

surrsysuni

∆H = - 890 kJ = - 890 000J

surrsysuni SSS

S /JK-1

+ve

-ve

spontaneous ∆Ssys = - 7

∆Ssurr = + 2986

= +

∆Suni = + 2979




Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


1148

298

)44100(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

118

18870

JKS

S

SSS

sys

sys

treacproductsys

130148118

JKS

SSS

uni

surrsysuni

∆H = -44.1 kJ = - 44 100J

surrsysuni SSS

S /JK-1

+ve

-ve

spontaneous

∆Ssys = - 118

∆Ssurr = + 148

= +

∆Suni = + 30


Condensation steam at 298K (25C) spontaneous?


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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 < 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


11463

298

)436000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

100

130230

JKS

S

SSS

sys

sys

treacproductsys

113631463100

JKS

SSS

uni

surrsysuni

∆H = + 436 kJ = + 436 000J

surrsysuni SSS

S /JK-1

+ve

-ve

non - spontaneous

∆Ssys = +100

∆Ssurr = - 1463

= +

∆Suni = - 1363


Is Atomization of H2 at 298K spontaneous?


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


120

298

)6000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

22

7048

JKS

S

SSS

sys

sys

treacproductsys

122022

JKS

SSS

uni

surrsysuni

∆H = -6 kJ = - 6000J

surrsysuni SSS

S /JK-1

+ve

-ve

non - spontaneous

∆Ssys = - 22

∆Ssurr = + 20

= + ∆Suni= - 2


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


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


18.22

263

)6000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

22

7048

JKS

S

SSS

sys

sys

treacproductsys

18.08.2222

JKS

SSS

uni

surrsysuni

∆H = -6 kJ = - 6000J

surrsysuni SSS

S /JK-1

+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

1 Quatitatively

T

H

T

QSsurr

Quatitatively

Entropy sys ↑ increase - More disorder - Gas form ↓

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


∆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


1597

298

)178000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

160

93253

JKS

S

SSS

sys

sys

treacproductsys

1437597160

JKS

SSS

uni

surrsysuni

∆H = + 178 kJ =+ 178 000J

surrsysuni SSS

S /JK-1

+ve

-ve

non - spontaneous

∆Ssys = + 160

∆Ssurr = - 597

= +

∆Suni= - 437


Decomposition CaCO3 at 298K (25C) spontaneous?


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

Quatitatively

Entropy sys ↑ increase - More disorder - Gas form ↓

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


∆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


1118

1500

)178000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

160

93253

JKS

S

SSS

sys

sys

treacproductsys

142118160

JKS

SSS

uni

surrsysuni

∆H = + 178 kJ =+ 178 000J

surrsysuni SSS

S /JK-1

+ve

-ve

spontaneous

∆Ssys = + 160

∆Ssurr = - 118

= + ∆Suni = + 42


Decomposition CaCO3 at 1500K (1227C) spontaneous?


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


1382

298

)114000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

42

522480

JKS

S

SSS

sys

sys

treacproductsys

133938242

JKS

SSS

uni

surrsysuni

∆H = - 114 kJ = - 114 000J

surrsysuni SSS

S /JK-1

+ve

-ve

spontaneous

∆Ssys = - 42

∆Ssurr = + 382

= +

∆Suni = + 339


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


Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


1308

298

)92000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

201

585384

JKS

S

SSS

sys

sys

treacproductsys

1107308201

JKS

SSS

uni

surrsysuni

∆H = - 92 kJ = - 92 000J

surrsysuni SSS

S /JK-1

+ve

-ve

spontaneous

∆Ssys = - 201

∆Ssurr = + 308

= +

∆Suni = + 107


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


NH3

Entropy


Entropy



X X X

1 Quatitatively

T

H

T

QSsurr

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


12855

298

)851000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

38

143105

JKS

S

SSS

sys

sys

treacproductsys

12817285538

JKS

SSS

uni

surrsysuni

∆H = - 851 kJ = - 851 000J

surrsysuni SSS

S /JK-1

+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

1 Quatitatively

T

H

T

QSsurr

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


1483

298

)144000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

37

572535

JKS

S

SSS

sys

sys

treacproductsys

144648337

JKS

SSS

uni

surrsysuni

∆H = - 144 kJ = - 144 000J

surrsysuni SSS

S /JK-1

+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

1 Quatitatively

T

H

T

QSsurr

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


19430

298

)2810000(

JKS

S

T

HS

surr

surr

surr

1

)tan()(

877

8211698

JKS

S

SSS

sys

sys

treacproductsys

1103079430877

JKS

SSS

uni

surrsysuni

∆H = - 2810 kJ = - 2810 000J

surrsysuni SSS

S /JK-1

+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






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






Law Thermodynamics


Unit - J mol -1 K-1





Temp = 298K

Non spontaneous

+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

Non spontaneous

H2(g) → 2 H(g) ∆H = + 436 kJ

Non spontaneous

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)

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

1

)tan()(

243

596353

JKS

S

SSS

sys

sys

treacproductsys

12990

298

)891000(

JKS

S

T

HS

surr

surr

surr

kJHsys 891)74(965

surrsysuni SSS

127472990243

JKS

SSS

uni

surrsysuni


Unit for ∆S - JK-1 Unit for ∆H - kJ



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 4 S0 +270 +205 x 5 +213 x 3 + 70 x 4

Reactant Product

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)


θ(pro) - ∑∆Hf

θ(react)

1

)tan()(

376

1295919

JKS

S

SSS

sys

sys

treacproductsys kJHsys 2219)104(2323

17446

298

)2219000(

JKS

S

T

HS

surr

surr

surr

surrsysuni SSS

170707446376

JKS

SSS

uni

surrsysuni



1 2

Entropy




X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

1

)tan()(

118

18870

JKS

S

SSS

sys

sys

treacproductsys

1148

298

)44000(

JKS

S

T

HS

surr

surr

surr

kJHsys 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)


θ(pro) - ∑∆Hf

θ(react)

1

)tan()(

22

7048

JKS

S

SSS

sys

sys


120

298

)6000(

JKS

S

T

HS

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 - 286 S0 + 188 + 70

H2O (l) → H2O(s) ∆Hf

0 - 286 - 292 S0 + 70 + 48

Entropy




X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

1308

298

)92000(

JKS

S

T

HS

surr

surr

surr

kJHsys 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)


θ(pro) - ∑∆Hf

θ(react)

kJHsys 168)1564(1732

1563

298

)168000(

JKS

S

T

HS

surr

surr

surr

surrsysuni SSS

152656337

JKS

SSS

uni

surrsysuni



5 6 N2(g) + 3H2(g) → 2NH3(g)

N2(g) + 3H2 (g) → 2NH3(g) ∆Hf

0 0 0 - 46 x 2 S0 + 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 - 436 S0 + 143 x 4 + 151 x 3 + 82

1

)tan()(

37

572535

JKS

S

SSS

sys

sys

treacproductsys

1118

1500

)178000(

JKS

S

T

HS

surr

surr

surr

Entropy




X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

θ(react)

kJHsys 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)


θ(pro) - ∑∆Hf

θ(react)

surrsysuni SSS

142118160

JKS

SSS

uni

surrsysuni



7 8 CaCO3 (s) → CaO(s) + CO2(g)

CaCO3 (s) → CaO (s) + CO2(g) ∆Hf

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

1

)tan()(

160

93253

JKS

S

SSS

sys

sys


Rxn Temp dependent Spontaneous at High ↑Temp

Decomposition limestone CaCO3 spontaneous?

1597

298

)178000(

JKS

S

T

HS

surr

surr

surr

Entropy




X X X

Reactant Product


θ(pro) - ∑∆Hf

θ(react)

∆Ssysθ = ∑Sf

θ(pro) - ∑Sf

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)


θ(pro) - ∑∆Hf

θ(react)

1

)tan()(

22

7048

JKS

S

SSS

sys

sys


18.22

263

)6000(

JKS

S

T

HS

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 - 292 S0 + 70 + 48


0 - 286 - 292 S0 + 70 + 48

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

Rxn Temp dependent Spontaneous at Low ↓ temp

120

298

)6000(

JKS

S

T

HS

surr

surr

surr

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 Product

S 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 Energy Microstate

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 More

Reactant Product

Qualitatively

Unit - J mol -1 K-1

Reactant Product

Entropy

Liq N2(l) Gas N2 (g)

Entropy




X X X

Qualitatively

Liquid → Gas

Reactant Product

S 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 Energy Microstate

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 ↑


Little change

Little change

2 3

4

Reactant Product

aq - 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 Product

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

Reactant Product

liq- more order g - more disorder S Lower ↓ S - Higher↑

Reactant Product

less g- more order more g - more disorder S Lower ↓ S - Higher↑

Reactant Product

Both sides equal number mol solid

Reactant Product

solid- more order aq - more disorder S Lower ↓ S - Higher↑

Reactant Product

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

5 6

7 8 9

IB Chemistry on Entropy and Laws of Thermodynamics

Education

Transcript of IB Chemistry on Entropy and Laws of Thermodynamics