# Homework Help: Phase Diagrams

1. Nov 17, 2013

### Qube

1. The problem statement, all variables and given/known data

https://scontent-b-dfw.xx.fbcdn.net/hphotos-prn1/v/1012733_10201076259690370_236735593_n.jpg?oh=4896ca67a34d3b223b764aba8ed308ab&oe=528A1B57

2. Relevant equations

3. The attempt at a solution

Not sure entirely what's going on here.

A) Triple point. Where the three states of matter exist in equilibrium.
B) Critical point. Where the distinction between liquid and gas ends. No more condensation or evaporation past this point. A supercritical fluid exists beyond this point.
C) Looks like a point within the solid region of the phase diagram.

These don't correspond with any answers. Boiling and melting points lie ON the 760 torr/1 atm dotted line, right? So it looks like there is no correct answer?!

ETA:

This seems to be a common "problem." Consider this follow up problem - er - what is this e to f line? Is there some convention I am missing - that there is always an implied e to f line?

https://scontent-b-dfw.xx.fbcdn.net/hphotos-frc1/v/576634_10201076272730696_868146875_n.jpg?oh=623c0ebd9b4868a62578d975129c85d3&oe=528A98A4

Also please consider this other problem in which there appear to be invisible points:

https://scontent-b-dfw.xx.fbcdn.net/hphotos-prn1/v/941858_10201076233729721_1666715440_n.jpg?oh=8f6cf59215279e3607fd06eb999ebedf&oe=528A8A74

Last edited: Nov 17, 2013
2. Nov 17, 2013

### Staff: Mentor

Looks like there is something wrong with the book.

3. Nov 17, 2013

### Qube

Right. I thought something was going over my head. Guess I'll take it up with the prof.

4. Nov 17, 2013

### Staff: Mentor

Is this taken from a text book or a past exam paper? If a book, maybe the editors got the figures jumbled up?

I'm uneasy where the question asks about lower-case points a, b and c but the nearest diagram is labelled in upper-case.

5. Nov 17, 2013

### Qube

These are actual past exam papers written by my professor and sold in a book. The problematic questions are also from separate years. I have no clue what is going on.

I might have to ask my prof for both clarification and refund on the price of purchasing his book.