AAMC #8 Q23 vs. ExamKrackers #29

[BlueMoon22]

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Hi all,

I had a question on AAMC #8 versus a similar question from the examkrackers gen. chem. book.

From EK G. Chem. #29:
A force is applied to a container of gas reducing its volume by half. The temperature of the gas:
A. decreases
B. increases
C. remains constant
D. The temperature change depends upon the amount of force used

From AAMC #8, #23:
The question went something like this: If the moles of gas remain the same while its temp. increases, what happens to the volume of gas?
Answer: Increases if pressure remains constant

In the EK question, if you attempt to use PV=nRT to solve the question, you will get the wrong answer. What EK was trying to get you to do was to use the fact that as you decrease the volume, the particles will bump into each other faster and thus increase temperature. This makes sense to me. However, how do you know not to use this logic on the AAMC question? With this logic, the answer to the AAMC question could have been decreases also.

I hope you guys understand my confusion here. Any help would be appreciated!

 

[BlueMoon22]

Bump!

 

[hplssrmantcxox]

EK question :
Work = P*deltaV = change in kinetic energy

Because you're applying a force onto the piston (i.e. doing work ON the system) you're "inputting" energy into the system. "inputting" more energy = more kinetic energy = higher temperature. It's kind of an involved question and really annoying... sigh.

The AAMC question wants you to simply just use PV=nRT or V/T = V/T without thinking about that energy theorem lol

 

[uclabruin8]

I think this has to do with Charles' Law: Volume and Temperature are directly proportional.