Phase Change and Lowest Boiling Point

AI Thread Summary
The discussion centers on the rationale behind selecting a gas for shock absorption under high pressure, specifically focusing on the question of why a gas with a lower boiling point, such as CO2, is preferred. The main concern is that gases can liquefy under high pressure, losing their compressibility and effectiveness as shock absorbers. The correct answer, CO2, is favored because it has the lowest boiling point among the options, which means it remains gaseous at lower temperatures and pressures. The confusion arises from the idea that a higher boiling point gas might be better since it would remain gaseous under more conditions. However, if a gas has a boiling point just below room temperature, it could condense under pressure, making it unsuitable. The discussion also touches on the impracticality of using water at room temperature in shock absorbers, emphasizing the need for a gas that remains in a gaseous state under varying conditions to maintain its shock-absorbing properties.
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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