Example 22 SI of CO2(g)

[jonji.yang@gmail.com]

Hello,

I am confusing myself going through example 22 trying to figure out the solubility of CO2 with pressure. From what I understand, we are adding CO2 to the system, allowing the fixed volume gas phase to increase in pressure. But the added CO2 should reach equilibrium between the aqueous and gas phases according to Henry's Law, correct? So why then does the SI of CO2(g) show as above 0?

Code: [Select]

------------------------------Saturation indices-------------------------------

  Phase               SI** log IAP   log K(298 K,  13 atm)

  CH4(g)         -117.53   -120.34   -2.81  CH4
  CO2(g)            1.09     -0.39   -1.48  CO2 Pressure  13.2 atm, phi 0.928
  H2(g)           -36.13    -39.24   -3.11  H2
  H2O(g)           -1.50     -0.00    1.50  H2O Pressure   0.0 atm, phi 0.878
  O2(g)           -11.02    -13.92   -2.90  O2

[dlparkhurst]

The SI for a gas component is the partial pressure (actually fugacity) of the gas component in the system.

Kh = a(CO2(aq)) / f(CO2(g))