# 11.12 - Lewis-Randall Rule and Henry's Law

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### Henry's Law (10:16)

Introduction to Henry's Law (10:16) (msu.edu)

Fugacities are calculated relative to standard state values, and the relations developed earlier in the chapter use a pure fluid standard state. What if the pure fluid does not exist as a liquid when pure? One choice is to use Henry's law.

### HenrysLaw:Estimation&amp;Validation

Henry's Law can be used to compute VLE of gases in solvents. We can estimate Henry's "constants" (uakron.edu, 12min) by Eqns. 11.64 and 11.68. Here we demonstrate the procedure for CO2+toluene and CO2+water. In some cases, the estimates can be good and in some cases they can be quite bad. The only way to know for sure is to validate your model with experimental data. Validation essentially involves finding data in the library and plotting on the same graph as the predictions. You should also compute the average deviations to provide a numerical measure of the goodness of fit.

Comprehension Questions:
1. Does the SCVP+ model predict higher or lower pure component fugacities than SCVP?
2. Why is it unusual for the deviations from Henry's Law to be positive?
3. Find experimental data for supercritical CO2+acetone. Identify the optimal value of A12 in the SCVP+M1 model to fit these data and compute the root mean square deviation (rmsd) of pressure: rmsd = sqrt(sum(Pcalc-Pexpt)^2).
4. Repeat 3 for N2+acetone. Compare the SCVP, SCVP+, and SCVP+MAB predictions as well as including experimental data.