Using the ideal gas law with two unknowns

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Discussion Overview

The discussion revolves around applying the ideal gas law to a problem involving a closed container of a single atom ideal gas. Participants are tasked with determining the pressure and temperature after the gas expands to a new volume, while navigating the complexities of the ideal gas equation and potential adiabatic conditions.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents the ideal gas equation and manipulates it to express pressure in terms of temperature, but expresses uncertainty about how to proceed due to the presence of two unknowns.
  • Another participant suggests that the expansion may be adiabatic, introducing a potential additional constraint on the gas behavior.
  • A participant attempts to calculate the new temperature using an adiabatic relation but arrives at a value that they believe is incorrect according to their lecturer.
  • A later reply reiterates the temperature calculation attempt, yielding a slightly different result, and questions the lecturer's perspective on the accuracy of their answers.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correct method to find the new temperature and pressure, with multiple competing approaches and results presented.

Contextual Notes

The discussion includes assumptions about the nature of the gas expansion (adiabatic vs. isothermal) and the dependence on the specific heat ratio, which are not fully resolved. There are also unresolved mathematical steps in the calculations presented.

Who May Find This Useful

Students and educators interested in the application of the ideal gas law, particularly in contexts involving changes in volume and temperature, may find this discussion relevant.

kaffekjele
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Homework Statement



You are given a closed container containing a single atom ideal gas.
The volume is V1= 0,45*10^(-3) m^3
Pressure p1 is 3,2 MPa
Temperature, T1, is 892 K

The volume of the gas is increased to V2= 8*V1

Find the pressure and temperature after the increase of volume.


Homework Equations



Ideal gas equation pV=nRT





The Attempt at a Solution



I have n= 0,19 moles from a previous question. R is the ideal gas constant, 8,31 J/moles*K

Manipulating the ideal gas equation for pressure gives me p = (nRT)/V but that leaves T as an unknown so I'm not sure if that's the right way to go...
 
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I would expect that the expansion is adiabatic, this gives another constraint on the gas.
 
I was looking at that and tried to find the new temperature by using T2= T1*(\frac{V1}{V2})\gamma-1 which gave me 221,46K which is not correct according to my lecturer.
 
It would be interesting to see how the lecturer would solve this.
 
kaffekjele said:
I was looking at that and tried to find the new temperature by using T2= T1*(\frac{V1}{V2})\gamma-1 which gave me 221,46K which is not correct according to my lecturer.

I get 223 K. What does your lecturer think about that answer?
 

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