Closed vs. Open System

[hredzak]

Okay, I understand the difference btw an open and closed system. But I have somewhat of an interesting case - where the solution is exposed to and interacting with external atmosphere which has circulated into the headspace of the beaker. But it's not an open system in a traditional sense... Would this still be considered an open system or closed?

[Tom Meuzelaar]

Okay, I understand the difference btw an open and closed system. But I have somewhat of an interesting case - where the solution is exposed to and interacting with external atmosphere which has circulated into the headspace of the beaker. But it's not an open system in a traditional sense... Would this still be considered an open system or closed?

Hi:

It depends on the question you are asking the model. If the gases in the headspace have already equilibrated with the solution, you can consider it a closed system. If, however, you are interested in knowing how the gases affect the composition of the fluid, you could model it as an open system. In other words, in the first scenario, the boundaries of your system encompass both the fluid and the headspace gases. In the second scenario, the boundaries of your system encompass the fluid only, while the headspace gases are external- gases can be transferred into or out of the system.

Keep in mind, also, that GWB tracks gas fugacities, and not actual masses.

I hope that helps,

Tom Meuzelaar

RockWare, Inc.