Solutions to exercises
301
In these conditions, the advantages of gradual internal reforming are
2 a strong decrease in water requirements, which simplifies the system and
its use,
2 delocalization of the thermal gradient due to the endothermicity of the
steam reforming reaction,
2 superior performance due to an increased emf of the cell.
In contrast, the operation without steam at the anode makes the system move
vulnerable to carbon deposits.
Solution 5.19 – Electrochemical integrator
1. Electrode (1), which is negatively polarized, is the site of a reduction
Ag
+ + e $ Ag
Electrode (2), which is positively polarized, is the site of an oxidation
Cl
−
$ 2
1
Cl 2 + e
2. a. The emf at the terminals of the cell is expressed as
E
2F
RT
ln P
P
Cl
(1)
Cl
(2)
2
2
Δ =
#
where P
( )
Cl
1
2
and P
( )
Cl
2
2
denote respectively the chlorine partial pressure in
compartments (1) and (2).
P
( )
Cl
1
2
corresponds to the equilibrium pressure of chlorine relative to the
formation reaction for AgCl (s)
Ag (s) + 2
1
Cl 2(g) m AgCl 2(s)
where we verify the expression P
e
Cl
(1)
2
RT
2 G
f T
=
D °
Δ f G T ° is the standard free enthalpy of the formation reaction of AgCl (s) at
temperature T.
P
( )
Cl
2
2
is obtained by using the ideal gas law
P
n
V
RT
( )
Cl
Cl
2
2
2
=
where V is the volume of the bulb and n Cl 2 is the number of moles of
chlorine produced by the current. Denoting by Q the charge that goes
through the cell, we can write