Problems and Solutions
Chapter 12
Enthalpy of Reaction and Chemical Equilibria
Textbook Examples:
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12.01
Enthalpy of Reaction of the Ammonia Synthesis in the Ideal
Gas State (p. 510)
Mathcad (2001) - Solution (zip)
Mathcad (2001) - Solution as XPS
12.02
Enthalpy of Reaction of the Ammonia Synthesis at Higher
Pressure Using VTPR (p. 511)
Mathcad Solution see 12.01
12.03
Equilibrium Constant and Equilibrium Conversion of the
Ammonia Synthesis Assuming Ideal Gas Behavior (p. 517)
Mathcad Solution see 12.01
12.04
Equilibrium Conversion of the Ammonia Synthesis Assuming
Real Gas Behavior Using SRK, PSRK and VTPR (p. 522)
Mathcad Solution see 12.01
12.05
MTBE-synthesis - Chemical Equilibrium in a Real Liquid
Mixture (p. 526)
Mathcad (2001) - Solution (zip)
Mathcad (2001) - Solution as XPS
12.06
Simultaneous Chemical Reaction Equilibria Via Relaxation -
Steam-Reforming (p. 535)
Mathcad (2001) - Solution (zip)
Mathcad (2001) - Solution as XPS
12.07
Molar Gibbs Energy as Function of Composition and
Equilibrium Concentration for then n-Butane – i-Butane Isomerization
Reaction (p. 538)
12.08
Simultaneous Chemical Reaction Equilibria Via Gibbs Energy
Minimization - Steam-Reforming (p. 541)
Mathcad (2001) - Solution (zip)
Mathcad (2001) - Solution as XPS
Additional Problems:
P12.01
Influence of n-Pentane on the Equilibrium Composition (TAME
Synthesis)
Calculate the equilibrium composition of the TAME (tert.
amylmethylether) synthesis in the liquid phase using equimolar amounts
of methanol (MeOH) and 2-methyl-2-butene (2M2B) at 25 and 80 °C
MeOH + 2M2B
⇆
TAME
with the help of the standard thermodynamic properties for the
ideal gas state given below
a)
without a solvent
b)
in the presence of
n-pentane with
nMeOH/npentane
= 1:1 and nMeOH/npentane = 1:4
Calculations should be performed
1) assuming ideal behavior; i.e.
gi
=1.
2) taking into account the real
behavior
and
a)
using the Wilson equation
b)
modified UNIFAC
Standard thermodynamic properties in the ideal gas state and Antoine
constants (log Pis (mm Hg) = A – B/(J
(°C) +C))
Parameters for the description of the molar heat capacities cP
for the ideal gas as a function of temperature (cP = a + bT +
cT2 +dT3)
Molar volumes and Wilson parameters for the compounds considered
P12.02 Influence
of Different Solvents on the Equilibrium Composition (TAME Synthesis)
For the TAME synthesis the influence of the equilibrium
conversion in the presence of the solvents benzene, THF and acetone in
the liquid phase should be calculated with the help of the modified
UNIFAC model at 80°C. The initial mixture should consist of equimolar
amounts of methanol (MeOH), 2-methyl-2-butene (2M2B), and solvent. All
required properties and parameters can be found in Example P12.01 and in
the Appendix.
P12.03
Equilibrium Conversion For Ethanol Synthesis From Ethylene and
Water
Ethanol can be produced from a feed of about 60 vol% ethylene and
40 vol% water. The mixture is reacted over a phosphoric acid catalyst at
300°C and 60 bar. Calculate the equilibrium constant at 25°C and 300°C
for this reaction. Calculate the effect of the real vapor phase behavior
on the equilibrium constant KP and equilibrium composition at
300°C as function of pressure up to a pressure of 100 bar using VTPR.The
standard thermodynamic data of formation and ideal gas heat capacity
correlations can be found in Appendix A.
P12.04
Equilibrium Constant of Ethane Dehydrogenation
At high temperatures, ethane dissociates via the reaction (ethane
cracker)
C2H6
C2H4
+ H2
Calculate
the equilibrium concentrations at T = 800 K and P = 2 bar. All required
data can be found in Appendix A.
P12.05
Optimal Feed Ratio (N2
to H2)
in Ammonia Synthesis Using Ideal Behavior and VTPR
Calculate the optimal feed ratio of nitrogen and hydrogen for the
ammonia synthesis at 450°C and a pressure of 600 atm using the
parameters given in examples 12.1 to 12.4 using
-
ideal gas behavior
- taking into account the real behavior using the VTPR group
contribution
equation of state
P12.06
Residual Part of the Heat Capacity of a Dissociative Gas
The dissociative gas and important rocket propellant dinitrogen
tetroxide is in rapid equilibrium with nitrogen dioxide following the
reaction:
N2O4
At a total pressure of 1 bar, the equilibrium concentration of N2O4
in the gas phase was reported to be 0.6349 (30°C), 0.4088 (50°C), 0.2113
(70°C), and 0.09321 (90°C). Calculate the residual part of the heat
capacity of the reactive mixture between 20°C and 100°C.
P12.07
Equilibrium Constant of the Oxyhydrogen Reaction
Calculate the equilibrium of water formation from the elements in
their most stable state for a stoichiometric feed of oxygen and hydrogen
at P = 0.01 Pa and T = 2000 K using the data from Appendix A and
assuming ideal gas phase behavior:
H2 + 0.5 O2
H2O
P12.08
Equilibrium Conversion of the Steam Reforming Process
In Example 12.6 the equilibrium conversion for the steam
reforming process was calculated for a water/methane ratio of 2.7 and a
pressure of 1 atm as a function of temperature. Please check how the
equilibrium conversion is changed, if the:
a)
water/methane ratio is changed to 2
b)
the reaction is performed at 5 atm