Find the final temperature? (Ideal Gas Law)

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Discussion Overview

The discussion revolves around a homework problem involving the Ideal Gas Law, specifically focusing on finding the final temperature of a gas given its initial conditions and a relationship between pressure and volume. The scope includes mathematical reasoning and technical explanation related to thermodynamics.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • Post 1 presents the initial conditions and the relationship between pressure and volume, seeking assistance in determining the final temperature.
  • Post 2 acknowledges the participant's work but suggests a potential mathematical error without specifying the details.
  • Post 3 requests clarification on where the mistake might be, indicating uncertainty about the calculations.
  • Post 4 reiterates that the final pressure is correct but questions the final temperature, implying a possible arithmetic error.
  • Post 5 points out that the calculated final temperature appears to be 4 K, questioning if this was the intended result.
  • Post 6 offers an alternative perspective, suggesting a possible oversight and providing a link to additional material for reference.
  • Post 7 concludes that the issue was indeed a math error and expresses gratitude for the assistance received.

Areas of Agreement / Disagreement

Participants generally agree that a mathematical error occurred in the calculations, but the specific nature of the error and the correct final temperature remain unresolved until the participant confirms their findings.

Contextual Notes

The discussion does not clarify the assumptions made regarding the gas behavior or the specific equations used, which may affect the interpretation of the results.

elephunk
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Homework Statement



Find the final temperature?

PV relationship -- PV^1.2 = constant

P1 = initial pressure = 720 kN/m^2
V1 = initial volume = 0.4 m^3
V2 = final volume = 1.2 m^3
T1 = initial temperature = 225 C

I managed to get the final pressure part out of the way but don't know where to head with the temperature. Can someone please point me in some direction?

Homework Equations


The Attempt at a Solution



The attempt at a solution and question can be found here: http://i45.photobucket.com/albums/f98/pastilles/Scan10012.jpg

Thanks for your help :)
 
Last edited by a moderator:
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Hi elephunk, welcome to the board. Your work looks good... you did it right but it looks like you made a mistake in the math.
 
Hi,

Thanks for the welcome :)

Can you point me to where I am going wrong? Maybe looking at this at nearly 1am in the morning isn't good :(
 
Your final pressure looks good, but your final temperature does not. The method seems correct, so it's probably a simple arithmetic error.
 
It looks from your attachment that you've calculated the final temperature to be 4 K. Is that what you meant the answer to be?
 
Your math seemed okay to me. What about this? Its been a while since Chem I but maybe??

http://img199.imageshack.us/img199/9922/scannedimage038.jpg
 
Last edited by a moderator:
Thanks. It was a math error.

Got it sorted now. Thanks all and thinks lizzyb for the the working out :)
 

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