Problems and Solutions
Chapter 7
Electrolyte Solutions
Textbook Examples:
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07.01
Molality to Mole Fraction Conversion for an Aqueous Sodium Chloride
Solution (p. 356)
07.02
Real Behavior in an Aqueous Caustic Soda Solution using the Chen NRTL
Model (p. 373)
07.03
Mean Ionic Activity Coefficient in an Aqueous Sodium Sulfate Solution
Using LIQUAC
(p. 381)
07.04
Osmotic Coefficient of Water in an Aqueous Sodium Sulfate Solution Using
LIQUAC
(p. 384)
07.05
Removal of a Calcium Sulfate Layer by Stepwise Addition of Sodium
Carbonate and Hydrogen Chloride
(p. 388)
Additional Problems:
P07.01
True Mole Fractions Assuming Total Dissociation
Calculate the mole fractions of all true species in a 0.1molal
aqueous solution of sodium thiosulfate assuming complete dissociation.
Is this a valid assumption?
P07.02
Mean Ionic Molality and Molal Ionic Strength Assuming Total
Dissociation
Calculate the mean ionic molality (Eq. 7.23) and the molal ionic
strength (Eq. 7.47) of a

1molal aqueous solution of hydrogen
chloride

0.01molal ethanolic solution of sulfuric
acid
assuming total dissociation of the electrolyte component.
P07.03 Water
Activity Coefficient in NaClSolution Derived From Osmotic Coefficients
(DDB)
Search the DDB (free Explorer Edition) for osmotic coefficients
for the system water – sodium chloride. From the data at 333K, calculate
the activity coefficient of the solvent water as function of the
molality of the salt.
P07.04
Solvent Activity Coefficient Derived From OsmoticCoefficients
(DDB)
Search the DDB (free Explorer Edition) for vaporliquid
equilibrium data for the system methanol – sodium chloride. Calculate
the activity coefficient of methanol as function of salt concentration.
P07.05 NaCl
Solubility in a Water KCl Mixture (DDB)
Search the DDB (free Explorer Edition) for salt solubility data
of sodium chloride in the system potassium chloride  water. Plot and
interpret the experimental data.
P07.06 Water
Saturation Pressure Over Aqueous NaOH Using Electrolyte NRTL
Calculate the saturation pressure of an aqueous NaOH solution at
J = 100°C at NaOH concentrations of
10, 30 and 50 wt.%. Use the Electrolyte NRTL model. The necessary
parameters are given in example 7.2.
P07.07 Saturation
Pressure Over an H_{2}SO_{4}
Solution Using Electrolyte NRTL
Calculate the saturation pressure of an aqueous H_{2}SO_{4}
solution at
J = 100°C at H_{2}SO_{4
}concentrations of 10, 30 and 50 wt.%. Use the Electrolyte NRTL
model. The required parameters can be downloaded from the textbook page
on www.ddbst.com.
P07.08
Liquid Heat Capacity of an NaCl Solution Using Electrolyte NRTL
Calculate the liquid heat capacity of a 20 wt.% NaCl solution at
J = 80°C using the Electrolyte NRTL
model. The required parameters can be downloaded from the textbook page
on www.ddbst.com.
P07.09 Saturation
Pressure of an Ammonia Solution Using the NRTL Equation and Electrolyte NRTL
Calculate the saturation pressure of a 20 wt.% ammonia solution
using the NRTL equation and the Electrolyte NRTL model at
J
= 20°C. An ideal vapor phase can be assumed. The pK_{b} value of
ammonia at 25°C is 4.75. Further required parameters can be downloaded
from the textbook page on www.ddbst.com. Do you think that the use of
the electrolyte model is necessary in this case? How is the situation
affected if significant amounts of CO_{2} are added to the
system?