TBR, Phases and Phase Change, Passage 4, pg 101 # 23

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Sammy1024

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23. Which of the following statements is NOT true?

A. It is possible to sublime the solidA form of Material C at temperatures below the first triple point by changing the pressure.

B. It is possible for gas of Material C to undergo deposition to solids at temperatures between the first and second triple points.

C. Both Material T and Material C have two triple points each.

D. At standard temperature and pressure (0"C and 1.00 atm.), Material T exists as solidA-


upload_2014-4-15_8-21-40.png


I picked C, because I looked at Material T and near the SolidA I see the solid and liquid intersecting, but didn't see how it was a triple point. Is it a triple point because Solid A, Solid B and Liquid are intersecting?

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Yes! A triple point by definition is where three distinct phases can co-exist. This graph actually has two triple points. The MCAT aims to test your understanding of very basic concepts, but on occasion that may be done using a highly unfamiliar example. Stay true to the fundamental concepts and try not to freak out, and you'll do quite well.
 
23. Which of the following statements is NOT true?

A. It is possible to sublime the solidA form of Material C at temperatures below the first triple point by changing the pressure.

B. It is possible for gas of Material C to undergo deposition to solids at temperatures between the first and second triple points.

C. Both Material T and Material C have two triple points each.

D. At standard temperature and pressure (0"C and 1.00 atm.), Material T exists as solidA-


View attachment 180319

I picked C, because I looked at Material T and near the SolidA I see the solid and liquid intersecting, but didn't see how it was a triple point. Is it a triple point because Solid A, Solid B and Liquid are intersecting?

yup. I had the same question. in thermo apparently, it's just a point where 3 phases intersect doesn't have to be solid/liquid/gas necessarily. many allotropes have two different versions of solids due to their lattice interactions.
 
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