Doubt in Raoultian and Henrian Standard State

$$Si(liq)=Si_\text{(1 wt% Fe)}$$

Can you describe what is going on here?All that they ask for is change in Gibbs free energy for the process.I am completely unable to figure why this particular model is so important for a specific question.It would be great if someone could interpret both the analytical and the mathematical analogy to this.There is also a difference between Raoultian and Henrian State which is to be applied here. I do not understand which one I am supposed to use when.Why is $$\text{1 wt% Fe}$$ so important?

• I don't have time to write a good answer, but maybe this will help. You can either write your own answer if it does or if it does not someone else might be able to. This should be the gibbs free energy of mixing. web.mst.edu/~billf/chap7.pdf – Tristan Maxson Jan 18 at 16:00