Phase Change and Lowest Boiling Point

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SUMMARY

The discussion centers on the rationale behind selecting gases for shock absorption, specifically focusing on the question of which gas has the lowest boiling point under high pressure conditions. The correct answer is carbon dioxide (CO2), which is preferred due to its low boiling point, allowing it to remain in gaseous form under pressure. The confusion arises from the assumption that a higher boiling point would be more advantageous; however, gases with lower boiling points are less likely to liquefy under pressure, maintaining their compressibility and effectiveness as shock absorbers.

PREREQUISITES
  • Understanding of gas laws and phase changes
  • Knowledge of boiling points and their implications in pressure scenarios
  • Familiarity with the properties of common gases like CO2, ammonia, and bromine
  • Basic principles of shock absorption mechanisms
NEXT STEPS
  • Research the properties of gases under varying pressure conditions
  • Study the phase diagrams of CO2 and other gases
  • Learn about the applications of gases in shock absorbers and other cushioning systems
  • Explore the implications of boiling points on gas behavior in engineering contexts
USEFUL FOR

This discussion is beneficial for students preparing for the MCAT, particularly those focusing on physical chemistry concepts, as well as engineers and scientists interested in the applications of gases in mechanical systems.

Dorj
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I am studying for the MCAT and I am having a hard time understanding the rationale for the following question from my review:

Q: One of the limitations of using a gas as a shock absorbing cushion is that under high pressure, the gas may liquefy and lose compressibility. Which of the following gases would be the best one to use in light of this concern? A. CO2, B. Water vapor, C. Bromine gas, D. Ammonia gas.

The correct answer was A as it had the lowest boiling point and the answer key just states that we want to pick the gas with the lowest boiling point, without explaining why. I am having a hard time understanding why, isn't it more reasonable to go with a gas with a higher boiling point in a high pressure situation, so that more of it remains in the gaseous form.

I am confused. Can someone please explain why lower bp is better in this context.
 
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What if its boiling point were just below room temperature? Wouldn't pressurizing it cause it to immediately condense? How about if its boiling point were even HIGHER that room temperature? Still a good gas for this application?
 
To put it differently - imagine filling a shock absorber wit water at room temperature. Would it work?
 

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