http://lawrencekok.blogspot.com
Prepared by Lawrence Kok
Tutorial on Entropy and 1st, 2nd and 3rd Law 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 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
∆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
∆E universe = ∆E sys + ∆E surrounding = 0
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
∆S uni = ∆S sys + ∆S surr
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
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
Why gas mixes and not unmix?
Why heat flow from hot to cold?
Notes on Entropy
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyedTransfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
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
∆S uni = ∆S sys + ∆S surr
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
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?
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Unit - J mol -1
K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0↓
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
Standard Molar Entropy, S0
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
Entropy perfectly crystal at 0K = 0↓
S0 when substance heated from 0K to 298K
Entropy
Why gas mix and not unmix?
Why solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Unit - J mol -1
K-1
Standard Molar Entropy, S0
Std state - 1 atm / 1M sol
Temp = 298K
Std Molar Entropy/S0
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
Standard Molar Entropy, S0
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 gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Less number gas↓
Entropy surr ↑ increase - Heat released 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
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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 7
∆Ssurr = + 2986
=+
∆Suni = + 2979
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Assume Q = H at constant pressure
Is Combustion at 298K spontaneous?
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Liquid form↓
Entropy surr ↑ increase - Heat released 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 - Condensation at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 118
∆Ssurr = + 148
=+
∆Suni = + 30
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Condensation steam at 298K (25C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
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
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
non - spontaneous
∆Ssys = +100
∆Ssurr = - 1463
=+
∆Suni = - 1363
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Atomization of H2 at 298K spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Solid form↓
Entropy surr ↑ increase - Heat released increase ↑ motion surr particles
↓Heat release by sys to surr increase ↑ entropy surr
↓∆S sys > ∆S surr (More -ve)
↓∆S uni = ∆S sys + ∆S surr
↓∆S uni < 0 - Freezing at 298K - Non Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
non - spontaneous
∆Ssys = - 22
∆Ssurr = + 20
=+∆Suni= - 2
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Freezing water to ice at 298K (25C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Solid form↓
Entropy surr ↑ increase - Heat released 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 - Freezing at 263K (-10C) - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 22
∆Ssurr = + 22.8
=+∆Suni= + 0.8
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Freezing water to ice at 263K (-10C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
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 = ∆S sys + ∆S surr
↓∆S uni < 0 - Decomposition at 298K - Non Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve non - spontaneous
∆Ssys = + 160
∆Ssurr = - 597
=+
∆Suni= - 437
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Decomposition CaCO3 at 298K (25C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
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 = ∆S sys + ∆S surr
↓∆S uni > 0 - Decomposition at 1500K - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = + 160
∆Ssurr = - 118
=+∆Suni = + 42
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Decomposition CaCO3 at 1500K (1227C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Less gas form↓
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 - Oxidation at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 42
∆Ssurr = + 382
=+∆Suni = + 339
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Oxidation of NO at 298K (25C) spontaneous?
Assume Q = H at constant pressure
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order - Less gas form↓
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 - NH3 production at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 201
∆Ssurr = + 308
=+∆Suni = + 107
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Haber, NH3 production 298K (25C) spontaneous?
Assume Q = H at constant pressure
NH3
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order ↓
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 - AI production at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys 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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 38
∆Ssurr = + 2855
=+
∆Suni = + 2817
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is Thermite, AI production 298K (25C) spontaneous?
Assume Q = H at constant pressure
Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) S0 + 87 + 28 x 2 + 27 x 2 + 51
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↓ decrease - More order ↓
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 - Decomposition KCIO3 at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys SSS
4KCIO3(s) → 3KCIO4(s) + KCI(s) ∆H = - 144 kJ at 298K
+ 572 + 535Reactant Product
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
surrsysuni SSS S /JK-1
+ve
-ve
spontaneous
∆Ssys = - 37
∆Ssurr = + 483
=+∆Suni = + 446
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is decomposition KCIO3
298K (25C) spontaneous?
Assume Q = H at constant pressure
∆S/∆H constant over range of temp
4KCIO3(s) → 3KCIO4(s) + KCI(s) S0 + 143 x 4 + 151 x 3 + 82
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixesSolution diffuse Heat flow hot →cold
X X X
1Quatitatively
TH
TQSsurr
Quatitatively
Entropy sys ↑ increase - More disorder ↓
Entropy surr ↑ increase - Heat release increase ↑ motion particles
↓Heat release by sys to surr increase ↑ entropy surr
↓∆S surr + ∆S sys > 0 (More +ve)
↓∆S uni = ∆S sys + ∆S surr
↓∆S uni > 0 Combustion sugar at 298K - Spontaneous
surrsysuni SSS
)tan()( treacprosys SSS
C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ at 298K
+ 821 + 1698Reactant Product
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
surrsysuni SSS S /JK-1
+ve
-ve spontaneous∆Ssys = + 877
∆Ssurr = + 9430
=+
∆Suni = + 10307
∆S uni > 0 (+ve) → Spontaneous ∆S uni < 0 (-ve) → Non spontaneous
Is combustion sugar 298K (25C) spontaneous?
Assume Q = H at constant pressure
∆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 = ∆S sys + ∆S surr
↓∆S uni > 0
∆S uni = ∆S sys + ∆S surr
↓∆S uni > 0
q = heat transfer
Isolated system ∆S uni always
increase
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyedTransfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
∆E = internal energy
w = work done
∆S = Entropy universe
∆S = Entropy system
∆S = Entropy surrounding
∆S uni = ∆S sys + ∆S surr
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
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)
Exothermic - Heat released
+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 = ∆S sys + ∆S surr
↓∆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 = ∆S sys + ∆S surr
↓∆S uni< 0
∆S uni = ∆S sys + ∆S surr
↓∆S uni < 0
∆S uni = ∆S sys + ∆S surr
↓∆S uni < 0
q = heat transfer
Isolated system ∆S uni always
increase
1st Law Thermodynamics 2nd Law Thermodynamics
Energy cannot be created or destroyedTransfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
∆E = internal energy
w = work done
∆S = Entropy universe
∆S = Entropy system
∆S = Entropy surrounding
∆S uni = ∆S sys + ∆S surr
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
Nonspontaneous
+ve
-ve=
S /JK-1
Endothermic - Heat absorb
∆Ssys = + ve
∆Ssurr = - ve∆Suni = - ve
+
∆S sys + ve , ∆S surr - ve↓
Suni < 0(Rxn always Non
spontaneous)
Exothermic - Heat released
+ve
-ve
∆Ssys = - ve
+
∆Ssurr = + ve
∆Suni = - ve=
∆S sys - ve, ∆S surr + ve↓
Suni < 0(Rxn Non
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 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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
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
Is Combustion at 298K spontaneous?
Unit for ∆S - JK-1 Unit for ∆H - kJ
∆S uni = ∆S sys + ∆S surr↓
∆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 = ∆S sys + ∆S surr↓
∆S uni > 0 - Combustion at 298K - Spontaneous
1 2
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)∆Ssys
θ = ∑Sfθ(pro) - ∑Sf
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 = ∆S sys + ∆S surr↓
∆S uni > 0 - Condensation at 298K - Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react) ∆Hsys
θ = ∑∆Hfθ(pro) - ∑∆Hf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJH sys 6)286(292
120298
)6000(
JKS
S
THS
surr
surr
surr
surrsysuni SSS
122022
JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr↓
∆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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)∆Ssys
θ = ∑Sfθ(pro) - ∑Sf
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 = ∆S sys + ∆S surr↓
∆S uni > 0 - NH3 production at 298K - Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react) ∆Hsys
θ = ∑∆Hfθ(pro) - ∑∆Hf
θ(react)
kJH sys 168)1564(1732
1563298
)168000(
JKS
S
THS
surr
surr
surr
surrsysuni SSS
152656337
JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr↓
∆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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)∆Ssys
θ = ∑Sfθ(pro) - ∑Sf
θ(react)
kJH sys 178)1206(1028
surrsysuni SSS
1437597160
JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr↓
∆S uni < 0 - Decomposition at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react) ∆Hsys
θ = ∑∆Hfθ(pro) - ∑∆Hf
θ(react)
surrsysuni SSS
142118160
JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr↓
∆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
treacproductsys kJH sys 178)1206(1028
Rxn Temp dependentSpontaneous at High ↑Temp
1500K (1227C)298K (25C)
Decomposition limestone CaCO3 spontaneous?
1597298
)178000(
JKS
S
THS
surr
surr
surr
Entropy
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - quatitatively
Gas mixesSolution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)∆Ssys
θ = ∑Sfθ(pro) - ∑Sf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJH sys 6)286(292
surrsysuni SSS
122022
JKS
SSS
uni
surrsysuni
Is Freezing spontaneous?
Unit for ∆S - JK-1 Unit for ∆H - kJ
∆S uni = ∆S sys + ∆S surr↓
∆S uni < 0 - Freezing at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react) ∆Hsys
θ = ∑∆Hfθ(pro) - ∑∆Hf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJH sys 6)286(292
18.22263
)6000(
JKS
S
THS
surr
surr
surr
surrsysuni SSS
18.08.2222
JKS
SSS
uni
surrsysuni
∆S uni = ∆S sys + ∆S surr↓
∆S uni > 0 -Freezing at 263K - Spontaneous
9 10 H2O (l) → H2O(s)
H2O (l) → H2O(s)
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292S0 + 70 + 48
H2O (l) → H2O(s) ∆Hf
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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Method to calculate entropy
Gas mixesSolution diffuse Heat flow hot →cold
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)
∆Ssysθ = More - Less
= +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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Method to calculate entropy
Gas mixesSolution diffuse Heat flow hot →cold
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)
∆Ssysθ = 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)
∆Ssysθ = More - Less
= +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
Why gas mixes and not unmix?
Why conc solution diffuse and not undiffuse?
Why heat flow from hot to cold?
Predict entropy change - qualitatively
Gas mixesSolution diffuse Heat flow hot →cold
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