1. Multireaction Stoichiometry
Jika terdapat dua atau lebih proses reaksi , maka digunakan ;
νi,j : the stoichiometric number of species i in reaction j.
the change of the moles of a species ni
i i jdn v d ,
j
j
i i i j n  n v  0 ,


n  n   v 
0 i ,
j 
j i , j  
i
j
j
j
j i



Dimana : (i= 1,2,….,N)
j n  n v  0
j
j

j

n 
v
i 0 i ,
j
j
j
j
j
i n v
y




0
integration
summation
total stoichiometric number

2. Example 13.3
Consider a system in which the following reactions occur,
4 2 2 CH  H OCO 3H 4 2 2 2 CH  2H OCO  4H
if there are present initially 2 mol CH4 and 3 mol H2O, determine expressions for the yi as
functions of ε1 and ε2 .
i CH4 H2O CO CO2 H2
j νj
1 -1 -1 1 0 3 2
2 -1 -2 0 1 4 2

j

n 
v
i 0 i ,
j
j
j
j
j
i n v
y




0
 
 
1 2
5  2 
2
1 2
2
 CH y
4  
3  
2
 
1 2
2 5  2  
2

1 2
 H O y

1
3  
4

 
1 2
5 2 2
2  

 CO y 1 2
5  2 
2
1 2
2
2 5  2  
2 
 CO y
1 2
 H y

3. Application of equilibrium criteria
to chemical reactions
Total enargi gibbs dari sistem tertutup pada P dan T konstan
dengan asumsi proses ireversible didapatkan. Pada keadaan
setimbang adalah
 dG
t  0
T,P

4. Application of equilibrium criteria
to chemical reactions
• ε is the single variable that characterizes the
progress of the reaction
• the total Gibbs energy at constant T and P is
determined by ε
• if not in chemical equilibrium, any reaction leads to a
decrease in the total Gibbs energy of the system
• The condition for equilibrium:
• the total Gibbs energy is a minimum
• Its differential is zero  dG
t  0
T,P G f ( ) t 

5. Standard Gibbs energy change
and the equilibrium constant
Dasar dari persamaan sistem single phase,
  
i i d(nG) (nV)dP (nS)dT  dn
i
dn v d i i 
Replaced by the product
  
i id(nG) (nV)dP (nS)dT   d
i
0
Persamaan differensial

nG G
 
( ) ( )

       



 
, ,





  at equilibrium
T P
t
 
i i
i T P

6. The fugacity of a species in solution:
i i i    (T) RTln fˆ
o
i G   (T)  RT ln f
For pure species i in its standard state: o
i i
ˆ
f
o i
o
i
G RT
   ln
i i f

 
 0 i i i
0
ˆ



f
o i
ln 




 
 G RT

i
o
i
i i f
0
ˆ

 

f
o i


ln 


  
i i
v
o
i
i i
i
f
 G RT

K
 
G
f
i

o G  G
 ˆ 

f i
RT
G
f
o
i i

i
v
i
o
i
i 



 

 

ln
 

 


RT
K
o
exp
f
i
v
o
i
i








ˆ
 
i
o
i i
Equlibrium state =0
exponential

7. 
 

 
 


G
RT
K
o
The equilibrium constant for the reaction, f(T) exp
o The standard Gibbs energy change of reaction, f(T) G  G
  
i
o
i i
o Other standard property changes of reaction : M  M
  
i
o
i i
RT
G
dT
d
H RT
o
i
o
i






  2
dT
RT
G
d
H RT
i
o
i i
i
o
i i


 



 

 



 2
 
dT
RT
d G
H RT
o
o

   2
Ho ln
d K
dT
RT
2 


8. For a chemical species in its standard state:
o
i
o
Gi  H TS
o
i
o
   
i
o
i i i
i i i
o
i i  G  H T  S
o o o G  H TS
summation

C

   
T
T
o
o o P dT
R
H H R
0
0

C

   
T
T
o
o o P
dT
T
R
S S R
0
0
H G
0 0
0 T
0
S
o o
o  
 
C
   
C



T
      
T
T
o
P
T
T
o
o o o o P
dT
T
R
dT RT
R
H G R
T
G H
0 0
0 0
0
0

9. C
   
C



T
      
T
T
o
P
T
T
o
o o o o P
dT
T
R
dT RT
R
H G R
T
G H
0 0
0 0
0
0
G
RT
K
o  
ln 
Readily calculated at any temperature from the standard
heat of reaction and the standard Gibbs energy change of
reaction at a reference temperature
0 1 2 K  K K K




  




G
0
0
0 exp
RT
K
o







1 exp 1








H


T
T
0
RT
K
o
0
0

 

 
 


C

T
   
T
o
P
T
T
o
P
dT
T
C
R
dT
R
T
K
0 0
1
exp 2