How Is Work Calculated in a Thermodynamic Process with Constant T2/V Ratio?

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Homework Help Overview

The discussion revolves around calculating work done in a thermodynamic process involving a bi-atomic ideal gas. The process maintains a constant ratio of temperature to volume while the temperature is doubled through combustion of methane.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to derive the work done during the transformation using the integral of pressure with respect to volume. They express uncertainty about which pressure value to use in the integral.
  • Some participants question the relationships between temperature, volume, and pressure, seeking to clarify how these variables interact in the context of the problem.
  • Others suggest expressing pressure as a function of the known variables before proceeding with integration.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the relationships between the variables involved. Guidance has been offered regarding expressing pressure in terms of other parameters, but no consensus has been reached on the approach to take for the work calculation.

Contextual Notes

The problem involves specific data and assumptions, such as the ideal gas behavior and the condition of no heat loss to the environment, which are under discussion but not fully resolved.

DottZakapa
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A volume VA contains n mole of a bi-atomic ideal gas, initially at temperature TA. Burning an amount M of methane, whose calorific power P (produced heat per unit mass while burning) is 13271 [kcal/kg], the temperature is slowly doubled, simultaneously expanding the volume in order to maintain the ratio (T2 / V) constant. Assuming that no heat is wasted in the environment.
DATA:
n= 0.3 [mole]; R= 0.082 [litre*atm/(mole*K)] ;
VA=9 [litre] ; TA=300 [K]; 1 [cal]=4.18[J]]

Following there is what I've solved so far:
PA=(nRTA)/ VA

TB= 2TA

VB=(TB2⋅VA)/ TA2= 4VA

PB=(nR2TA)/ 4VA

Considering that pressure and temperature aren't constant during the transformation, I'm not sure which value instead of pressure I have to insert in the integral in order to evaluate the work during the transformation.

W=∫ p⋅dV

I guess that I shall use this relation :

T2 / V = TA2 / VA

The solution to this is :

W=∫ p⋅dV=2nRTA

but I don't get how.
Could somebody help me with this?
Thanks
 
Last edited:
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How are T, V, TA, and VA related?

In terms of TA, VA, and n, what is the initial pressure pA?

What is the pressure when the volume is V?

Chet
 
Chestermiller said:
How are T, V, TA, and VA related?

In terms of TA, VA, and n, what is the initial pressure pA?

What is the pressure when the volume is V?

Chet
I've edited the template
 
Express p as a function of n, TA, VA and V. Then integrate.

Chet
 

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