IB Chemistry on Gibbs Free Energy vs Entropy on spontaniety
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Transcript of IB Chemistry on Gibbs Free Energy vs Entropy on spontaniety
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
∆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 ↑
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
Measure molecular disorder/randomness ↓
More disorder - More dispersion of matter/energy ↓
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
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 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
∆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 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
∆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
High chaos factor
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
Measure 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 destroyed Transfer from one form to another
∆E universe = ∆E sys + ∆E surrounding = 0
∆E = q + w
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
∆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 = 0 Std molar entropy, S0 (absolute value)
↓ 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?
High chaos factor
Entropy
Why gas mix and not unmix? Why solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
Unit - J mol -1 K-1
Standard Molar Entropy, S0
Entropy perfectly crystal at 0K = 0 (Absolute value) ↓
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 0K All sub > 0K, have +ve S0
Entropy perfectly crystal at 0K = 0 (Absolute value) ↓
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 mixes Solution 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 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
∆Hf θ (reactant) ∆Hf
θ (product)
Using Std ∆Hf θ formation to find ∆H rxn
∆H when 1 mol form from its element under std condition
Na(s) + ½ CI2(g) → NaCI (s) ∆Hf θ = - 411 kJ mol -1
Std Enthalpy Changes ∆Hθ
Std condition
Pressure 100kPa
Temp 298K
Conc 1M All substance at std states
Std ∆Hf θ formation
Mg(s) + ½ O2(g) → MgO(s) ∆Hf θ =- 602 kJ mol -1
Reactants Products
O2(g) → O2 (g) ∆Hf θ = 0 kJ mol -1
∆Hrxnθ = ∑∆Hf
θ(products) - ∑∆Hf
θ(reactants)
∆Hf θ (products) ∆Hf
θ (reactants)
∆Hrxnθ
Elements
Std state solid gas
2C(s) + 3H2(g)+ ½O2(g) → C2H5OH(I) ∆Hf θ =- 275 kJ mol -1
1 mole formed
H2(g) + ½O2(g) → H2O(I) ∆Hf θ =- 286 kJ mol -1
Std state solid gas 1 mol liquid
For element Std ∆Hf θ formation = 0
Mg(s)→ Mg(s) ∆Hf θ = 0 kJ mol -1
No product form
Using Std ∆Hf θ formation to find ∆H rxn
Click here chem database (std formation enthalpy)
Click here chem database (std formation enthalpy)
C2H4 + H2 C2H6
Find ΔHθ rxn using std ∆H formation
Reactants Products
2C + 3H2
Elements C2H4 + H2 → C2H6
∆Hrxnθ
∆Hrxnθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Hrxnθ = Hf
θ C2H6 - ∆Hf
θ C2H4+ H2 = - 84.6 – ( + 52.3 + 0 ) = - 136.9 kJ mol -1
Enthalpy Formation, ∆Hf
Std ∆Gfθ formation
∆Grxnθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Grxnθ = Gf
θ C2H6 - ∆Gf
θ C2H4+ H2 = - 33 – ( + 68 + 0 ) = - 101 kJ mol -1
∆Gf θ (reactant) ∆Gf
θ (product)
Using Std ∆Gf θ formation to find ∆G rxn o
∆Gf when 1 mol form from its element under std condition
Na(s) + ½ CI2(g) → NaCI (s) ∆Gf θ = - 384 kJ mol -1
Std Free Energy Change ∆Gθ
Std condition
Pressure 100kPa
Temp 298K
Conc 1M All substance at std states
Gibbs Free Energy change formation, ∆Gf
Mg(s) + ½ O2(g) → MgO(s) ∆Gf θ =- 560 kJ mol -1
Reactants Products
O2(g) → O2 (g) ∆Gf θ = 0 kJ mol -1
∆Grxnθ = ∑∆Gf
θ(prod) - ∑∆Gf
θ(react)
∆Gf θ (product) ∆Gf
θ (reactant)
∆Grxnθ
Elements
Std state solid gas
2C(s) + 3H2(g)+ ½O2(g) → C2H5OH(I) ∆Gf θ =- 175 kJ mol -1
1 mole formed
H2(g) + ½O2(g) → H2O(I) ∆Gf θ =- 237 kJ mol -1
Std state solid gas 1 mol liquid
For element Std ∆Gf θ formation = 0
Mg(s)→ Mg(s) ∆Gf θ = 0 kJ mol -1
No product form
Using Std ∆Gf θ formation to find ∆G rxn
Click here chem database (std ∆G formation)
Click here chem database (std ∆G formation)
C2H4 + H2 C2H6
Find ΔGθ rxn using std ∆G0 formation
Reactants Products
2C + 3H2
Elements C2H4 + H2 → C2H6
∆Grxnθ
∆S sys + ve , ∆S surr - ve
↓ ∆S uni > 0 (+ve)
(Rxn Spontaneous)
∆S sys - ve , ∆S surr + ve
↓ ∆S uni < 0 (-ve)
(Rxn Non spontaneous)
spontaneous
+ve
-ve
=
S /JK-1
∆Ssys = + ve
∆Ssurr = + ve
∆Suni = + ve
+
∆Ssys = - ve
+
∆Ssurr = + ve
∆Suni = + ve
= spontaneous
S /JK-1 S /JK-1
∆Ssys = + ve
+
∆Ssurr = - ve
=
∆Suni = + ve
spontaneous
C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l)
Using ∆Hsys , ∆Suni , ∆S sys , ∆S surr to predict spontaneity
2NO(g) + O2(g) → 2NO2(g) CaCO3 (s) → CaO(s) + CO2(g)
∆H = -ve (Heat released)
Difficult !!
∆S sys + ve , ∆S surr - ve
↓ ∆S uni < 0 (-ve)
(Rxn Non spontaneous)
∆Ssys = + ve
∆Ssurr = - ve
+ =
∆Suni = - ve
Non spontaneous
∆H = -ve (Heat released) ∆H = +ve (Heat absorb)
CaCO3 (s) → CaO(s) + CO2(g)
∆H = +ve (Heat absorb)
∆Ssys = + ve
+
∆Ssurr = - ve
∆Suni = - ve
Non spontaneous
=
H2(g) → 2 H(g)
∆H = +ve (Heat absorb)
H2O (l) → H2O(s)
∆H = -ve (Heat released)
∆Ssys = - ve
+
∆Suni = - ve
∆Ssurr = + ve
=
∆S sys + ve , ∆S surr - ve
↓ ∆S uni < 0 (-ve)
(Rxn Non spontaneous)
∆S sys + ve , ∆S surr + ve
↓ ∆S uni > 0 (+ve)
(Rxn Spontaneous)
∆S sys - ve , ∆S surr + ve
↓ ∆S uni > 0 (+ve)
(Rxn Spontaneous)
∆Hsys ∆Ssys ∆Suni Description
- + > 0 (+) Spontaneous, All Temp
+ - < 0 (-) Non spontaneous, All Temp
+ + > 0 (+) Spontaneous, High ↑ Temp
- - > 0 (+) Spontaneous, Low ↓ Temp
Predicting Spontaneity rxn
∆G - Temp/Pressure remain constant Assume ∆S/∆H constant with temp
Using ∆Hsys , ∆Suni , ∆S sys , ∆S surr to predict spontaneity Using ∆Gsys to predict spontaneity
syssyssys STHG
Difficult !!
surrsysuni SSS T
HSsurr
)()( reactfprofsys HHH
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 + 171 x 2
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
1
)tan()(
41
596555
JKS
S
SSS
sys
sys
treacproductsys kJHsys 891)74(965
12990
298
)891000(
JKS
S
T
HS
surr
surr
surr
12949299041
JKS
SSS
uni
surrsysuni
∆S uni > 0 spontaneous
Easier
Unit ∆G - kJ Unit ∆S - JK-1
Unit ∆H - kJ
CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)
Only ∆S sys involved ∆S surr, ∆S uni not needed
∆Hsys ∆Ssys ∆Gsys Description
- + ∆G = ∆H - T∆S
∆G = - ve Spontaneous, All Temp
+ - ∆G = ∆H - T∆S
∆G = + ve Non spontaneous, All Temp
+ + ∆G = ∆H - T∆S
∆G = - ve Spontaneous, High ↑ Temp
- - ∆G = ∆H - T∆S
∆G = - ve Spontaneous, Low ↓ Temp
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g) S0 + 186 +205 x 2 +213 + 188 x 2
Reactant (+596) Product (+589)
kJG
G
STHG syssyssys
888
)007.0(298890
∆Hsys = - 890 kJ kJS
JKS
S
SSS
sys
sys
sys
reactprodsys
007.0
7
596589
1
)()(
∆G < 0 spontaneous
Entropy change ∆S greater at low temp
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -868 - (-51) = - 817 kJ
Predicting Spontaneity rxn
∆G - Temp/Pressure remain constant Assume ∆S/∆H constant with temp
Using ∆Gsys to predict spontaneity
syssyssys STHG
CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)
Reactant (-51) Product (-868)
∆G < 0 spontaneous
Easier
Unit ∆G - kJ mol-1 CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)
Only ∆S sys involved ∆S surr, ∆S uni not needed
∆Hsys ∆Ssys ∆Gsys Description
- + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at all Temp
+ - ∆G = ∆H - T ∆S
∆G = + ve Non spontaneous, all Temp
+ + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at high ↑ Temp
- - ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at low ↓ Temp
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g) S0 + 186 +205 x 2 +213 + 188 x 2
Reactant (+ 596) Product (+ 589)
kJG
G
STHG syssyssys
888
)007.0(298890
∆Hsys = - 890 kJ kJS
JKS
S
SSS
sys
sys
sys
reactprodsys
007.0
7
596589
1
)()(
∆G < 0 spontaneous
Using ∆Gsys to predict spontaneity
Easier
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(l) ∆G0 - 51 0 - 394 - 237 x 2
Method 1 Method 2
)()( reactfprofsys GGG
CH4(g) + 2 O2 (g) CO2(g) + 2H2O(g)
C + 2O2 + 2H2
Reactants Products ∆Gsys
θ
∆Gf θ (reactant) ∆Gf
θ (product) Elements
• Neither ∆H or ∆S can predict feasibility of spontaneous rxn • Gibbs Free Energy (∆G) – measure spontaneity and useful energy available • Gibbs Free Energy (∆G) - max amt useful work at constant Temp/Pressure • Involve ∆H sys and ∆S sys • ∆G involve only sys while ∆S uni involve sys and surr • Easier to find ∆H and ∆S for system
Gibbs Free Energy change formation, ∆Gf0
At std condition/states Temp - 298K Press - 1 atm
∆G - Temp/Pressure remain constant Assume ∆S/∆H constant with temp
Using ∆Gsys to predict spontaneity
syssyssys STHG
Easier
Unit ∆G - kJ CH4(g) + 2O2 (g) → CO2(g) + 2H2O(l)
Only ∆S sys involved ∆S surr, ∆S uni not needed
∆Hsys ∆Ssys ∆Gsys Description
- + ∆G = ∆H - T∆S
∆G = - ve Spontaneous, All Temp
+ - ∆G = ∆H - T∆S
∆G = + ve Non spontaneous, All Temp
+ + ∆G = ∆H - T∆S
∆G = - ve Spontaneous, High ↑ Temp
- - ∆G = ∆H - T∆S
∆G = - ve Spontaneous, Low ↓ Temp
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g) S0 + 186 +205 x 2 +213 + 188 x 2
Reactant (+ 596) Product (+ 589)
kJG
G
G
STHG syssyssys
888
2890
)007.0(298890
∆Hsys = - 890 kJ
kJS
JKS
S
SSS
sys
sys
sys
reactprodsys
007.0
7
596589
1
)()(
∆G < 0 spontaneous
Gibbs Free Energy Change, ∆G
∆G sys T∆S sys
Total energy change, ∆H
Measure spontaneity and useful energy available Max amt useful work at constant Temp/Pressure
Free Energy
syssyssys STHG
Free energy available to do work not available
for work
syssyssys STHG
Free Energy
Total energy change, ∆H
∆G sys T∆S sys
-890kJ
Free energy available to do work
not available for work
-888kJ +2 kJ
Gibbs Free Energy Change, ∆G
∆G - Temp/Pressure remain constant Assume ∆S/∆H constant with temp
Using ∆Gsys to predict spontaneity
syssyssys STHG
Easier
Unit ∆G - kJ mol-1
Only ∆S sys involved ∆S surr, ∆S uni not needed
Using ∆Gsys to predict spontaneity
Easier
Method 1 Method 2
)()( reactfprofsys GGG At std condition/states
Temp - 298K Press - 1 atm
Gibbs Free Energy change formation, ∆Gf0
At High Temp ↑
Temp dependent
syssyssys STHG
At low Temp ↓
veG
STG
HST sys
syssyssys STHG
veG
HG
STH
spontaneous spontaneous
surrsysuni SSS
T
HS
sys
surr
syssysuni STHST
Deriving Gibbs Free Energy Change, ∆G
T
HSS
sys
sysuni
∆S sys / ∆H sys
multi by -T
syssyssys STHG
∆Hsys ∆Ssys ∆Gsys Description
- + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at all Temp
+ - ∆G = ∆H - T ∆S
∆G = + ve Non spontaneous, all Temp
unisys STG syssyssys STHG
Only ∆H sys/∆S sys involved ∆S surr, ∆S uni not needed
syssyssys STHG
Non standard condition Standard condition
or
Gibbs Free Energy Change, ∆G
syssyssys STHG unisys STG
veGsys
∆S uni = +ve
Spontaneous Spontaneous
veGsys ∆H = - ve
∆S sys = +ve
∆Hsys ∆Ssys ∆Gsys Description
+ + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at high ↑ Temp
- - ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at low ↓ Temp
kJG
G
STHG
130
)16.0(298178
Predict entropy change - quatitatively
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJHsys 178)1206(1028
∆G uni > 0 - Decomposition at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
CaCO3 (s) → CaO(s) + CO2(g)
CaCO3 (s) → CaO (s) + CO2(g) ∆Hf
0 - 1206 - 635 - 393 S0 + 93 + 40 + 213
kJS
S
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
)tan()(
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
kJHsys 178)1206(1028
Rxn Temp dependent Spontaneous at High ↑ temp
Decomposition limestone CaCO3 spontaneous?
Gibbs Free Energy Change, ∆G
kJS
S
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
)tan()(
kJG
G
STHG
62
)16.0(1500178
∆G uni < 0 - Decomposition at 1500K - Spontaneous
∆H = +ve ∆S = +ve
Temp dependent
∆Hsys ∆Ssys ∆Gsys Description
+ + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at high ↑ Temp
- - ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at low ↓ Temp
At Low Temp At High Temp
Predict entropy change - quatitatively
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆G uni > 0 - Decomposition at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
Rxn Temp dependent Spontaneous at Low ↓ temp
Gibbs Free Energy Change, ∆G
∆G uni < 0 - Decomposition at 1500K - Spontaneous
∆H = - ve ∆S = - ve
Temp dependent
∆Hsys ∆Ssys ∆Gsys Description
+ + ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at high ↑ Temp
- - ∆G = ∆H - T ∆S
∆G = - ve Spontaneous at low ↓ Temp
H2O (l) → H2O(s)
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292 S0 + 70 + 48
Freezing at 298K (25C)
Is Freezing spontaneous?
kJHsys 6)286(292
kJS
S
S
SSS
sys
sys
sys
treacproductsys
02.0
22
7048
)tan()(
kJG
G
STHG
55.0
)022.0(2986
Freezing at 263K (-10C)
H2O (l) → H2O(s)
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292 S0 + 70 + 48
kJHsys 6)286(292
kJS
S
S
SSS
sys
sys
sys
treacproductsys
02.0
22
7048
)tan()(
kJG
G
STHG
21.0
)022.0(2636
At High Temp At Low Temp
C3H8(g) + 5 O2 (g) 3CO2(g) + 4H2O(l)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
1
syssyssys STHG
)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
kJG
G
STHG
2108
)376.0(2982220
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
376.0
376
1295919
1
)tan()(
∆H = -2220 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Is Combustion at 298K spontaneous?
Using Free Energy to predict spontaneity
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -2130 - (-23) = - 2153 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Combustion at 298K - Spontaneous
C3H8(g) + 5 O2 (g) → 3 CO2(g) + 4 H2O(l) ∆G0 - 23 0 - 394 x 3 - 237 x 4
Elements
3C + 5O2 + 4H2
Reactant (-23) Product (-2130)
∆G < 0 - Combustion at 298K - Spontaneous
CH4(g) + 2O2 (g) → CO2(g) + 2H2O(g) ∆H = - 890 kJ at 298K
CH4(g) + 2 O2 (g) CO2(g) + 2H2O(g)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
2
syssyssys STHG
)tan()( treacprosys SSS
+ 596 + 589 Reactant Product
kJG
G
STHG
888
)007.0(298890
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
007.0
7
596589
1
)tan()(
∆H = - 890 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Is Combustion at 298K spontaneous?
Using Free Energy to predict spontaneity
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -868 - (-51) = - 817 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Combustion at 298K - Spontaneous
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(l) ∆G0 - 51 0 - 394 - 237 x 2
Elements
C + 2O2 + 2H2
Reactant (-51) Product (-868)
∆G < 0 - Combustion at 298K - Spontaneous
CH4(g) + 2 O2 (g) → CO2(g) + 2 H2O(g) S0 + 186 +205 x 2 +213 + 188 x 2
H2O (g) → H2O(l) ∆H = - 44.1 kJ at 298K
H2O(g) H2O(l)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 188 + 70 Reactant Product
kJG
G
STHG
1.9
)118.0(2981.44
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
118.0
118
18870
1
)tan()(
∆H = - 44.1 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -237 - (-228) = - 9 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Combustion at 298K - Spontaneous
H2O(g) → H2O(l) ∆G0 -228 - 237
Elements
H2 + O2
Reactant (-228) Product (-237)
∆G < 0 - Combustion at 298K - Spontaneous
Condensation steam at 298K (25C) spontaneous?
H2O (g) → H2O(l) S0 + 188 + 70
3
Using Free Energy to predict spontaneity
H2(g) → 2 H(g) ∆H = + 436 kJ at 298K
H2(g) 2H(g)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 130 + 230 Reactant Product
kJG
G
STHG
406
)1.0(298436
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
1.0
100
130230
1
)tan()(
∆H = + 436 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = + 406 - (0) = +406 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G > 0 - Atomization at 298K - Non Spontaneous
H2(g) → 2H(g) ∆G0 0 + 203 x 2
Elements
H2
Reactant (0) Product ( + 406)
4 Is Atomization of H2 at 298K spontaneous?
H2 (g) → 2 H(g) S0 + 130 + 115 x 2
∆G > 0 - Atomization at 298K - Non Spontaneous
Using Free Energy to predict spontaneity
H2O (l) → H2O(s) ∆H = - 6 kJ at 298K
H2O(l) H2O(s)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
2
syssyssys STHG
)tan()( treacprosys SSS
+ 70 + 48 Reactant Product
kJG
G
STHG
55.0
)022.0(2986
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
022.0
22
7048
1
)tan()(
∆H = - 6 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -236.6 - (-237) = + 0.4kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G > 0 -Freezing at 298K - Non Spontaneous
H2O(l) → H2O(s) ∆G0 -237 - 236.6
Elements
H2 + O2
Reactant (-237) Product (-236.6)
5
H2O (l) → H2O(s) S0 + 70 + 48
∆G > 0 -Freezing at 298K - Non Spontaneous
Is Freezing water to ice at 298K (25C) spontaneous?
Using Free Energy to predict spontaneity
H2O (l) → H2O(s) ∆H = - 6 kJ at 263K
H2O(l) H2O(s)
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
2
syssyssys STHG
)tan()( treacprosys SSS
+ 70 + 48 Reactant Product
kJG
G
STHG
21.0
)022.0(2636
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
022.0
22
7048
1
)tan()(
∆H = - 6 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -237.2 - (-237) = - 0.2 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 -Freezing at 263K - Spontaneous
H2O(l) → H2O(s) ∆G0 -237 - 237.2
Elements
H2 + O2
Reactant (-237) Product (-237.2)
6
H2O (l) → H2O(s) S0 + 70 + 48
∆G < 0 -Freezing at 263K - Spontaneous
Is Freezing water to ice at 263K (-10C) spontaneous?
Assume std condition at 263K
Using Free Energy to predict spontaneity
CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 298K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 93 + 253 Reactant Product
kJG
G
STHG
130
)16.0(298178
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
1
)tan()(
∆H = + 178 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = - 999 - (- 1129) = + 130 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G > 0 - Decomposition at 298K - Non Spontaneous
CaCO3(s) → CaO + CO2(g) ∆G0 -1129 - 604 - 395
Elements
Ca + C + O2
Reactant ( -1129) Product (- 999)
7 Decomposition CaCO3 at 298K (25C) spontaneous?
CaCO3 (s) → CaO (s) + CO2(g) S0 + 93 + 40 + 213
∆G > 0 - Decomposition at 298K - Non Spontaneous
CaCO3 (s) CaO (s) + CO2(g)
Using Free Energy to predict spontaneity
CaCO3 (s) → CaO(s) + CO2(g) ∆H = + 178 kJ at 1500K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 93 + 253 Reactant Product
kJG
G
STHG
62
)16.0(1500178
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
1
)tan()(
∆H = + 178 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = - 999 - (- 939) = - 60 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Decomposition at 1500K - Spontaneous
CaCO3(s) → CaO + CO2(g) ∆G0 -939 - 604 - 395
Elements
Ca + C + O2
Reactant (- 939) Product (- 999)
8
CaCO3 (s) → CaO (s) + CO2(g) S0 + 93 + 40 + 213
CaCO3 (s) CaO (s) + CO2(g)
Decomposition CaCO3 at 1500K (1227C) spontaneous?
∆G < 0 - Decomposition at 1500K - Spontaneous
Assume std condition at 1500K
Using Free Energy to predict spontaneity
2NO(g) + O2(g) → 2NO2(g) ∆H = - 114 kJ at 298K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 522 + 480 Reactant Product
kJG
G
STHG
101
)042.0(298114
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
042.0
42
522480
1
)tan()(
∆H = - 114 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = + 104 - (174) = - 70 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Decomposition at 298K - Spontaneous
2 NO + O2 → 2NO2(g) ∆G0 + 87 x 2 0 + 52 x 2
Elements
N2 + O2
Reactant (+ 174) Product (+ 104)
9
2 NO(g) + O2 (g) 2NO2(g)
∆G < 0 - Decomposition at 298K - Spontaneous
Is Oxidation of NO at 298K (25C) spontaneous?
2 NO(g) + O2 (g) → 2NO2(g) S0 + 210 x 2 + 102 + 240 x 2
Using Free Energy to predict spontaneity
N2(g) + 3H2(g) → 2NH3(g) ∆H = - 92 kJ at 298K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 585 + 384 Reactant Product
kJG
G
STHG
32
)2.0(29892
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
2.0
201
585384
1
)tan()(
∆H = - 92 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = - 34 - (0) = - 34 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - NH3 production at 298K - Spontaneous
N2 + 3H2 → 2NH3(g) ∆G0 0 0 - 17 x 2
Elements
N2 + H2
Reactant (0) Product (- 34)
10
N2(g) + 3H2 (g) 2NH3(g)
Is Haber, NH3 production 298K (25C) spontaneous?
NH3
N2(g) + 3H2 (g) → 2NH3(g) S0 + 192 + 131 x 3 + 192 x 2
∆G < 0 - NH3 production at 298K - Spontaneous
Using Free Energy to predict spontaneity
Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) ∆H = - 851 kJ at 298K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 143 + 105 Reactant Product
kJG
G
STHG
840
)038.0(298851
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
038.0
38
143105
1
)tan()(
∆H = - 851 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -1576 - (-741) = - 835 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - AI production at 298K - Spontaneous
Fe2O3 + 2AI → 2Fe + AI2O3 ∆G0 - 741 0 0 - 1576
Elements
Fe + AI + O2
Reactant (-741) Product (- 1576)
11 Is Thermite, AI production 298K (25C) spontaneous?
Fe2O3(s) + 2AI(s) → 2Fe(s) + AI2O3(s) S0 + 87 + 28 x 2 + 27 x 2 + 51
∆G < 0 - AI production at 298K - Spontaneous
Fe2O3(s) + 2AI(s) 2Fe(s) + AI2O3(s)
Using Free Energy to predict spontaneity
4KCIO3(s) → 3KCIO4(s) + KCI(s) ∆H = - 144 kJ at 298K
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 572 + 535 Reactant Product
kJG
G
STHG
133
)037.0(298144
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
037.0
37
572535
1
)tan()(
∆H = - 144 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -1317 - (-1160) = - 157 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 - Decomposition at 298K - Spontaneous
4KCIO3 → 3 KCIO4 + KCI ∆G0 - 290 x 4 - 303 x 3 - 408
Elements
K + CI2 + O2
Reactant (-1160) Product (- 1317)
13
∆G < 0 - Decomposition at 298K - Spontaneous
Is decomposition KCIO3
298K (25C) spontaneous?
4KCIO3(s) → 3KCIO4(s) + KCI(s) S0 + 143 x 4 + 151 x 3 + 82
4KCIO3(s) 3KCIO4(s) + KCI(s)
Using Free Energy to predict spontaneity
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Will rxn be spontaneous ?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
syssyssys STHG
)tan()( treacprosys SSS
+ 821 + 1698 Reactant Product
kJG
G
STHG
3071
)877.0(2982810
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
877.0
877
8211698
1
)tan()(
∆H = - 2810 kJ
Assume ∆S, ∆H at constant over Temp
∆G sys < 0 (-ve) → Spontaneous ∆G sys > 0 (+ve) → Non spontaneous
Gibbs Free Energy, ∆G
syssyssys STHG
Unit ∆S - JK-1
Unit ∆H - kJ Unit ∆G - kJ
Reactants Products
∆Gsysθ = ∑∆Gf
θ(pro) - ∑∆Gf
θ(react)
∆Gsysθ = -3792 - (-910) = - 2882 kJ
∆Gsysθ
∆Gf θ (reactant) ∆Gf
θ (product)
)()( reactfprofsys GGG
∆G < 0 Combustion sugar at 298K - Spontaneous
Elements
C + H2 + O2
Reactant (-910) Product (- 3792)
14
Is combustion sugar
298K (25C) spontaneous? C6H12O6(s) + 6O2 (g) → 6CO2(g) + 6H2O(l) ∆H = - 2810 kJ at 298K
C6H12O6 (s) + 6O2(g) → 6CO2(g) + 6H2O(l) S0 + 209 +102 x 6 + 213 x 6 + 70 x 6
∆G < 0 Combustion sugar at 298K - Spontaneous
C6H12O6 + 6O2 6CO2 + 6H2O(l)
C6H12O6 (s) + 6O2(g) → 6CO2(g) + 6H2O(l) ∆G0 - 910 0 - 395 x 6 - 237 x 6
Using Free Energy to predict spontaneity
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Predict ∆G change - quatitatively
Gas mixes Solution 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 + 171 x 2
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
041.0
41
596555
1
)tan()(
kJH sys 890)74(964
Is Combustion at 298K spontaneous?
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 + 171 x 4
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
028.0
28
12951323
1
)tan()(
kJHsys 2219)104(2323
1 2
kJG
G
STHG
877
)041.0(298890
∆G < 0 Combustion sugar at 298K - Spontaneous
kJG
G
STHG
881
)028.0(2982219
∆G < 0 Combustion sugar at 298K - Spontaneous
Entropy and Gibbs Free Energy
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
118.0
118
18870
1
)tan()(
kJHsys 44)242(286
Is Condensation/Freezing at 298K spontaneous?
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
022.0
22
7048
1
)tan()(
kJHsys 6)286(292
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
kJG
G
STHG
1.9
)118.0(2981.44
∆G < 0 Condensation at 298K - Spontaneous
kJG
G
STHG
55.0
)022.0(2986
∆G > 0 Freezing at 298K – Non Spontaneous
Entropy and Gibbs Free Energy
Predict ∆G change - quatitatively
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJHsys 92)0(92
Are these rxn at 298K spontaneous?
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsys
θ = ∑∆Hfθ
(pro) - ∑∆Hfθ
(react)
kJHsys 168)1564(1732
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
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
201.0
201
585384
1
)tan()(
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
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
037.0
37
572535
1
)tan()(
kJG
G
STHG
32
)2.0(29892
∆G < 0 NH3 production at 298K - Spontaneous
kJG
G
STHG
157
)037.0(298168
∆G < 0 KCIO3 production at 298K - Spontaneous
Entropy and Gibbs Free Energy
Predict ∆G change - quatitatively
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJHsys 178)1206(1028
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsys
θ = ∑∆Hfθ
(pro) - ∑∆Hfθ
(react)
7 8 CaCO3 (s) → CaO(s) + CO2(g)
CaCO3 (s) → CaO (s) + CO2(g) ∆Hf
0 - 1206 - 635 - 393 S0 + 93 + 40 + 213
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
1
)tan()(
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
kJHsys 178)1206(1028
Rxn Temp dependent Spontaneous at High ↑ temp
Decomposition limestone CaCO3 spontaneous?
kJG
G
STHG
130
)16.0(298178
∆G > 0 Decomposition at 298K – Non Spontaneous
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
16.0
160
93253
1
)tan()(
kJG
G
STHG
62
)16.0(1500178
∆G < 0 Decomposition at 1500 K - Spontaneous
At Low Temp At High Temp
Entropy and Gibbs Free Energy
Predict ∆G change - quatitatively
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Gas mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
022.0
22
7048
1
)tan()(
kJHsys 6)286(292
Is Freezing spontaneous?
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
kJS
JKS
S
SSS
sys
sys
sys
treacproductsys
022.0
22
7048
1
)tan()(
kJHsys 6)286(292
9 10 H2O (l) → H2O(s) H2O (l) → H2O(s)
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292 S0 + 70 + 48
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292 S0 + 70 + 48
Freezing at 298K (25C) Freezing at 263K (-10C)
Rxn Temp dependent Spontaneous at Low ↓ temp
kJG
G
STHG
55.0
)022.0(2986
∆G > 0 Freezing at 298K – Non Spontaneous
kJG
G
STHG
21.0
)022.0(2636
∆G < 0 Freezing at 263K – Spontaneous
At High Temp At Low Temp
Entropy and Gibbs Free Energy
Predict ∆G change - quatitatively
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 mixes Solution diffuse Heat flow hot →cold
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
Why gas mixes and not unmix? Why conc solution diffuse and not undiffuse? Why heat flow from hot to cold?
Entropy
Thermodynamic Entropy
Gas mixes Solution diffuse Heat flow hot →cold
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 ↓
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
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 = ∆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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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
18.22
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
∆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 mixes Solution diffuse Heat flow hot →cold
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 ↓
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
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 ↓
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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 + 105 Reactant Product
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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 + 535 Reactant Product
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
1 Quatitatively
T
H
T
QSsurr
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 + 1698 Reactant Product
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
∆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
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 mixes Solution 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)
∆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
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 4 S0 +270 +205 x 5 +213 x 3 + 70 x 4
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
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
∆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 mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
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 = ∆S sys + ∆S surr ↓
∆S uni > 0 - Condensation at 298K - Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292
120
298
)6000(
JKS
S
T
HS
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 - 286 S0 + 188 + 70
H2O (l) → H2O(s) ∆Hf
0 - 286 - 292 S0 + 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 mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
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 = ∆S sys + ∆S surr ↓
∆S uni > 0 - NH3 production at 298K - Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
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
∆S uni = ∆S sys + ∆S surr ↓
∆S uni > 0 - Decomposition at 298K - Spontaneous
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
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 mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
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 = ∆S sys + ∆S surr ↓
∆S uni < 0 - Decomposition at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(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 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
treacproductsys kJHsys 178)1206(1028
Rxn Temp dependent Spontaneous at High ↑Temp
Decomposition limestone CaCO3 spontaneous?
1597
298
)178000(
JKS
S
T
HS
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 mixes Solution diffuse Heat flow hot →cold
X X X
Reactant Product
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292
surrsysuni SSS
122022
JKS
SSS
uni
surrsysuni
Is Freezing spontaneous?
∆S uni = ∆S sys + ∆S surr ↓
∆S uni < 0 - Freezing at 298K - Non Spontaneous
Reactant Product
∆Ssysθ = ∑Sf
θ(pro) - ∑Sf
θ(react)
∆Hsysθ = ∑∆Hf
θ(pro) - ∑∆Hf
θ(react)
1
)tan()(
22
7048
JKS
S
SSS
sys
sys
treacproductsys kJHsys 6)286(292
18.22
263
)6000(
JKS
S
T
HS
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 - 292 S0 + 70 + 48
H2O (l) → H2O(s) ∆Hf
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