Graph - critical point

[brood910]

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SPOILER ALERT.

I couldnt edit the title.
This question is from AAMC chem self-assessment. So DONT scroll down if you do not want to see this.

D is the critical point.. I know what "critical point" is and where it is in the normal pressure vs temperature graph.. but I cant really figure out how to read this graph..

Can anyone help with this?

 

[inasensegone]

Where'd you get this graph?

It seems like the other lines (line A) are there to throw you off. Beyond a critical point, the substance is a supercritical fluid, and it has properties of both a liquid and a gas. This would make sense that it is above the point where both liquid + vapor exist, because the critical point exists at a higher pressure, and has properties of both. The volume it takes up is also similarly between the volume of a liquid, and the volume of a vapor, because it has properties of both. A vapor has higher volume than a liquid, and this is reflected in the graph. The supercritical fluid then, must be somewhere between the two and at a higher pressure (just as in the regular pressure vs temperature graph)

 

[brood910]

Where'd you get this graph?

It seems like the other lines (line A) are there to throw you off. Beyond a critical point, the substance is a supercritical fluid, and it has properties of both a liquid and a gas. This would make sense that it is above the point where both liquid + vapor exist, because the critical point exists at a higher pressure, and has properties of both. The volume it takes up is also similarly between the volume of a liquid, and the volume of a vapor, because it has properties of both. A vapor has higher volume than a liquid, and this is reflected in the graph. The supercritical fluid then, must be somewhere between the two and at a higher pressure (just as in the regular pressure vs temperature graph)

It's from AAMC chem self assessment.
Thanks for the help, as usual!

 

[inasensegone]

It's from AAMC chem self assessment.
Thanks for the help, as usual!

Lol awww weak! Spoiler alert! Haha... I was hoping to avoid seeing any of these until I'm done with content review 🙂

And no problem, it's the least I can do as I've read a lot of your posts that ended up answering some of my questions 🙂

 

[brood910]

Lol awww weak! Spoiler alert! Haha... I was hoping to avoid seeing any of these until I'm done with content review 🙂

And no problem, it's the least I can do as I've read a lot of your posts that ended up answering some of my questions 🙂

Yeah, I tried to edit the title because of that, but I realized I couldnt. Sorry D:

 

[scrub2scrubs]

Just thought that I would add something. Normally on a pressure volume curve, those horizontal lines represent "isotherms" or places where the temperature is the same. The higher up an isotherm is, the higher the temperature. Idk if it actually helps in solving the question though.

 

[Blueprint MCAT Tutor]

Heya, great question!

I typed up a really extensive reply with lots of pictures here:

(spoilers aplenty, of course)
http://forums.studentdoctor.net/threads/aamc-questions-the-whole-thread-is-spoilers.1057364/