Two 1-liter flasks are at different temperatures; initially the left flask contains 500 mL of water with dissolved salt and the right flask contains 200 mL of pure water. You can control the temperature of the left flask and the amount of salt dissolved with sliders. Click the play button “go to equilibrium” to remove the caps on each flask. 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. Note that water transfers much faster in the simulation than in the physical process. Check “show fugacities” to display the water fugacities in each flask.
The saturation pressure of water $P^{sat}$ is calculated using the Antoine equation:
$$P^{sat} = 10^{A - \frac{B}{T+C}},$$
where $A$, $B$ and $C$ are Antoine constants, $T$ is temperature (°C) and $P^{sat}$ is in units of kPa.
The fugacity $f$ of pure water is equal to its saturation pressure:
$$f = P^{sat}(T).$$
For water with dissolved salt, the fugacity of the solution $\hat{f}$ (kPa) is given by:
$$\hat{f} = x f = x P^{sat}(T),$$
where $x$ is the mole fraction of water.
This simulation was created in the Department of Chemical and Biological Engineering at University of Colorado Boulder for LearnChemE.com by John L. Falconer using Claude AI. It is a JavaScript/HTML5 implementation of a Mathematica simulation by Rachael L. Baumann. It was prepared with financial support from the National Science Foundation (DUE 2336987 and 2336988). Address any questions or comments to LearnChemE@gmail.com.