Pxy Diagram

[anthropos]

I have difficulty understanding the Pxy diagram of a binary system (e.g. an ideal benzene-toulene mixture) and some facts in general, have been stuck there for hours, reading notes and everything but never seem to find or understand it.

 

1) Why is the bubble point line the line that indicates the total pressure of the system (partial pressure of benzene and toulene vapours)?

 

2) Why is the dew point curve and how do I derive it, because I really have no idea.

 

3) When I say a liquid is saturated, it means it's in equilibrium with the vapor, or is it 100% liquid. Then this means the vapor is saturated as well? But there is a graph with P against specific volume that depicts a maximum curve, one of the two sides being the saturated liquid line, and the other being the saturated vapour line and they are not together.

 

Gah please help thanks, I am dying to know.