Thermo: Need help finding T2 and V2 in an adiabat

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Homework Help Overview

The discussion revolves around an adiabatic compression of 1 mole of an ideal gas, initially at 294 K and 0.83 atm, being compressed to 10.0 atm. Participants are tasked with finding the final temperature and volume, as well as changes in internal energy, enthalpy, and work done during the process.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the use of the ideal gas law and the adiabatic condition, questioning the relevance of specific heat in the context of changing volume. There is an exploration of how to relate initial and final states using the adiabatic condition.

Discussion Status

Some participants have made initial calculations for the volume and are considering the implications of the adiabatic condition. There is an ongoing exploration of how to apply these principles to find the unknowns, with no explicit consensus reached yet.

Contextual Notes

Participants note the need to use the adiabatic condition and express uncertainty about how to proceed with multiple unknowns in the calculations.

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Homework Statement



1 mole of ideal gas initially at 294 K is compressed adiabatically and
reversibly from 0.83 atm to 10.0 atm. Calculate the initial and …final volumes,
the final temperature, [itex]\Delta[/itex]U; [itex]\Delta[/itex]H; Q; and W: Assume that Cv = (5/2)R

Given:

n = 1 mol
T1 = 294 K
P1 = 0.83 atm
P2 = 10 atm
Q = 0

Find
V1, V2, [itex]\Delta[/itex]U, Q, [itex]\Delta[/itex]H, T2, W

Homework Equations



1. The professor gave that specific heat at constant volume is (5/2)R, however, the volume of the problem changes. Is this equation completely irrelevant to the problem?

2. How to you find the final temperature and final volume?


The Attempt at a Solution



I started off with PV = nRT for the initial givens and obtained that V1 = 29.1 L

Now, I'm stuck. I've tried using the ideal gas equation again, but I have 2 unknowns. I tried rearranging the equation and setting it equal the initial equations. I know how to find the other unknowns, but I'm stuck at this part for some reason.
 
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Courtknee said:

Homework Statement



1 mole of ideal gas initially at 294 K is compressed adiabatically and
reversibly from 0.83 atm to 10.0 atm. Calculate the initial and …final volumes,
the final temperature, [itex]\Delta[/itex]U; [itex]\Delta[/itex]H; Q; and W: Assume that Cv = (5/2)R

Given:

n = 1 mol
T1 = 294 K
P1 = 0.83 atm
P2 = 10 atm
Q = 0

Find
V1, V2, [itex]\Delta[/itex]U, Q, [itex]\Delta[/itex]H, T2, W

Homework Equations



1. The professor gave that specific heat at constant volume is (5/2)R, however, the volume of the problem changes. Is this equation completely irrelevant to the problem?

2. How to you find the final temperature and final volume?

The Attempt at a Solution



I started off with PV = nRT for the initial givens and obtained that V1 = 29.1 L

Now, I'm stuck. I've tried using the ideal gas equation again, but I have 2 unknowns. I tried rearranging the equation and setting it equal the initial equations. I know how to find the other unknowns, but I'm stuck at this part for some reason.
You need to use the adiabatic condition: [itex]PV^\gamma = constant = K[/itex] which can be rewritten: [itex]TV^{\gamma-1} = K/nR = constant[/itex]

AM
 
I'm assuming that the constant K will remain the same for p1*v1 and p2*v2

If I set P1V1γ = K, then I can use that constant for P2V2γ and obtain the volume, correct?
 
Courtknee said:
I'm assuming that the constant K will remain the same for p1*v1 and p2*v2
If it didn't, it would not be constant!

If I set P1V1γ = K, then I can use that constant for P2V2γ and obtain the volume, correct?
Exactly.

AM
 

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