Calculate Pressure When V2 Changes: PVT Relationships

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Discussion Overview

The discussion revolves around calculating pressure in a gas system when the volume changes, specifically using the ideal gas law and the combined gas equation. The context includes theoretical applications of gas laws and problem-solving related to pressure, volume, and temperature changes.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant asks how to calculate pressure when the volume changes, providing initial conditions for pressure, volume, and temperature.
  • Another participant requests clarification on the type of fluid involved in the problem.
  • A participant assumes the ideal gas law will be used to solve the problem.
  • One participant suggests a pressure of 8 atm but expresses uncertainty about the calculation method.
  • Another participant explains the ideal gas law and notes that the mass of the gas is needed to determine the parameters for state 2.
  • One participant mentions the combined gas equation, indicating that it simplifies the problem without needing to know mass or the gas constant initially.
  • A later reply confirms they have resolved the problem with the assistance of others.

Areas of Agreement / Disagreement

Participants generally agree on using the ideal gas law and the combined gas equation, but there is no consensus on the specific calculation method or the final pressure value.

Contextual Notes

The discussion lacks details on the assumptions made regarding the gas behavior and the specific conditions under which the ideal gas law applies. There is also an absence of clarity on the mass of the gas, which is crucial for determining the pressure accurately.

db1
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How do i calculate pressure?

P1 = 3atm .... P2 = ?
V1 = 4 m3...V2 = 2 m3(half original)
T1 = 300k...T2 = 400

how do i calculate pressure when V2 changes?

Thanks for any help
 
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You need to give a bit more on the problem? What fluid are you using?
 
just says a quantity of gas
 
I'll assume that they want to use the ideal gas law to solve then.
 
P2 = 8atm, I am just not sure how to work it out
 
You have a gas at two states; let's call it state 1 and state 2.

Ideal gas law is pV=mRT where R is universal gas constant of 8314.

You have all the parameters for state 1 apart from the mass. Once you know this you will know all the parameters for state 2 apart from the pressure. Plug in the numbers and there's your answer.
 
its just talking about the combined gas equation PV/T= constant

it isn't saying anything about m or R yet
 
Well then it is even easier!

PV/t=constant so for state 1, obtain an aswer (this is constant) then rearrange for V and plug in the values for state 2.
 
have it now, thanks for your help
 

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