Weak Electrolyte Thermodynamics

1
Weak Electrolyte Thermodynamics

• Gas solubility in water
• Henrys Law
• Works well for nonpolar species (N2, O2, He,
  etc.)
• What about CO2?
• Henrys Law alone fails why?
• What happens in solution?
• CO2 H2O ? HCO3- H
• HCO3- ? CO3-2 H
• Chemical reactions/interactions enhance/augment
  phase equilibrium for weak electrolyte systems
  (CO2, NH3, SO2, HCN, H2S, etc.)

2
Weak Electrolyte Thermodynamics

• Practical example
• Urea production
• Aqueous mixture of NH3, CO2, and H2O

VAPOR
CO2(v) NH3(v) H2O(v)
CO2(l) NH3(l) H2O(l)
NH3(l) H2O(l) ? NH4 OH- CO2(l) H2O(l) ?
HCO3- H HCO3- ? CO3-2 H NH3(l) HCO3- ?
NH2COO- H2O(l) H2O(l) ? H OH-
LIQUID