Solving Part B of PV=NkbT: An Explanation

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Homework Help Overview

The discussion revolves around the application of the ideal gas law (PV=NkbT) and the calculation of change in entropy in a thermodynamic context. The original poster attempts to solve part B of a problem related to microstates and macrostates, specifically addressing the implications of a very small volume raised to the power of the number of atoms.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the implications of calculating V^N and its relationship to entropy. Questions arise regarding the definition of "Macrostate" and the validity of the equations used, particularly in the context of undefined values such as ln(0).

Discussion Status

Participants are exploring different interpretations of the problem, with some suggesting that the numerical value of V^N is relative and may depend on unit choices. Others question the formulation of the entropy equation and the meaning of "Macrostate," indicating a productive direction for further inquiry.

Contextual Notes

The original poster notes a potential error in their calculation due to the undefined nature of ln(0) when attempting to calculate change in entropy. There is also a mention of missing information regarding the specific question being addressed.

Junkwisch
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Homework Statement



"see attachment"

Homework Equations



PV=NkbT
Change in entropy = Boltzmann Constant x In(Macrostate)

The Attempt at a Solution



for part A, I knew that PV=NKbT

giving that pressure is 101300Pa volume is 1*10^-3 m^3, Kb is 1.38*10^-23 and T=300K
I find N to be 2.446*10^22 atoms


the problem I have is with part B

the question states that microstate is proportion to V^N where N is the number of atom I found in part A, and V is the volume which is 1*10-9 m^3. Thus V^N is a very small number which is pretty much zero. Change in entropy = Boltzmann Constant x In(Macrostate), since Macrostate is zero, there is an error in this calculation. Since In(0) is undefined. What am I suppose to do in this question??
 
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I forgot to attach the question, here it is
 

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Hi Junkwisch!

Always in physics things are only big or small relative to other things. The numerical value of V^N depends entirely on what units you're using.

Perhaps you can simplify \ln\left(V^N\right) without making an approximation? :smile:
 
Junkwisch said:
Change in entropy = Boltzmann Constant x In(Macrostate)
You should check that you have the correct relationship here. How can the left side of the equation be a change when there's no corresponding change present on the righthand side of the equation? Also, what is "Macrostate" supposed to represent?
 

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