Fugacity as a Driving Force for Mass Transfer
Two 1-liter flasks are at different temperatures; the left flask contains water with dissolved salt and the right flask contains pure water. You can control the temperature of the left flask and the amount of salt dissolved with sliders. Select the reset button and then select play ("go to equilibrium"). Water transfers from one flask to the other to try to make water fugacities equal in each flask. For some conditions, all the water transfers to the left or right flask. Check "show fugacities" to display the water fugacities in each flask.

Download the CDF file to view the simulation using the free Wolfram CDF player.