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 0.1-molal 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 
-          1-molal aqueous solution of hydrogen chloride
-          0.01-molal ethanolic solution of sulfuric acid
assuming total dissociation of the electrolyte component.

P07.03        Water Activity Coefficient in NaCl-Solution 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.
solution video  (large), (medium), (small)

P07.04         Solvent Activity Coefficient Derived From OsmoticCoefficients (DDB)

Search the DDB (free Explorer Edition) for vapor-liquid equilibrium data for the system methanol – sodium chloride. Calculate the activity coefficient of methanol as function of salt concentration.
solution video  (large), (medium), (small)

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.
solution video  (large), (medium), (small)

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 H2SO4 Solution Using Electrolyte NRTL

Calculate the saturation pressure of an aqueous H2SO4 solution at J = 100°C at H2SO4 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 pKb 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 CO2 are added to the system?