How Do You Solve This Thermodynamics Ideal Gas Law Problem?

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Homework Help Overview

The discussion revolves around a thermodynamics problem involving an ideal monatomic gas contained in a cylinder, transitioning through various states (A, B, C) with specified volume and pressure conditions. The participants are exploring the implications of the Ideal Gas Law in determining the pressure at state C and discussing the nature of the thermodynamic cycle.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to apply the Ideal Gas Law to find the pressure at state C, with some questioning the implications of constant volume and the relationship between states A, B, and C. There is also discussion on the temperature changes and their effects on pressure.

Discussion Status

The discussion is active, with participants offering guidance on applying the Ideal Gas Law and clarifying the relationships between the states. There is acknowledgment of the need to determine temperature at state B and how it relates to the pressure at state C.

Contextual Notes

Participants are working under the constraints of the problem statement, which includes specific conditions for each state and the requirement to justify answers regarding work done and the nature of the device (refrigerator or heat engine).

science.girl
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Homework Statement



A cylinder contains 2 moles of an ideal monatomic gas that is initially at state A with a volume of 1.0 x 10-2 m3 and a pressure of 4.0 x 105 Pa.
The gas is brought isobarically to state B. where the volume is 2.0 x 10-2 m3.
The gas is then brought at constant volume to state C, where its temperature is the same as at state A. The gas is then brought isothermally back to state A.

a. Determine the pressure of the gas at state C.

b. State whether the net work done by the gas during the complete cycle is positive, negative, or zero. Justify your answer.

c. State whether this device is a refrigerator or a heat engine. Justify your answer.


Homework Equations


PV = nRT


The Attempt at a Solution



Well, I have points A and B on a PV diagram. I need to figure out the pressure of the gas at state C to proceed.

I know I have to apply the Ideal Gas Law, but I'm just not sure how. Any help?
 
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science.girl said:
The gas is brought isobarically to state B. where the volume is 2.0 x 10-2 m3.
The gas is then brought at constant volume to state C, where its temperature is the same as at state A. The gas is then brought isothermally back to state A.

The gas was brought at constant volume to state C correct? So if the gas was brought to C at constant volume, that means it didnt change, so it has to have the same volume as it did in step B.
 
science.girl said:

Homework Equations


PV = nRT

The Attempt at a Solution



Well, I have points A and B on a PV diagram. I need to figure out the pressure of the gas at state C to proceed.

I know I have to apply the Ideal Gas Law, but I'm just not sure how. Any help?
You have the right equation. What is the temperature at B? (apply ideal gas law). What is the change in temperature in going to C? Apply the ideal gas law again to get the change in pressure from B to C.

AM
 
wow, sorry for my useless post. for some reason i read it as your problem being you weren't sure what the volume was at C. Follow Andrews steps.
 
Andrew Mason said:
You have the right equation. What is the temperature at B? (apply ideal gas law). What is the change in temperature in going to C? Apply the ideal gas law again to get the change in pressure from B to C.

AM

Thank you for your help, Andrew. :smile:
 

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