Entropy of Ideal Gas N2 at 350 K, 2.0 bar

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Homework Help Overview

The discussion revolves around calculating the entropy of 1.0 litre of gaseous N2 at a temperature of 350 K and a pressure of 2.0 bar, using a reference entropy value at standard conditions. The problem involves thermodynamic principles related to ideal gases.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the use of an equation relating entropy change to temperature and pressure, questioning the applicability of the formula when pressure is not constant. There is also discussion about the specific heat capacity at constant pressure and its relevance in this context.

Discussion Status

Some participants have provided guidance on the integration approach to isolate entropy, while others are questioning the assumptions regarding constant pressure and the nature of specific heat capacity in this scenario. Multiple interpretations of the problem are being explored without a clear consensus.

Contextual Notes

There is uncertainty regarding the value of the specific heat capacity, C_p, and whether it can be applied under changing pressure conditions. The original poster has noted the lack of information on C_p, which is critical for the calculations.

mahdert
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Homework Statement



what is the entropy of 1.0 litre of gasoues n2 at Ta=350 K and Pa=2.0 bar given that So = 191.61 J/(K gmol) at To = 298.15 K and Po = 1 bar?

Homework Equations


I think : S(at 350) - So = NC_p ln (Ta/To) - NR ln(Pa/po)


The Attempt at a Solution


My problem is, C_p is not given and can we use this formula if p is not constant.
 
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1) Are you sure you don't know c_P for an ideal gas?
2) To see if you can use this equation even if P is changing, how about starting from dU=T\,dS-P\,dV, isolating dS, and integrating?
 
C_p = 5/2 R;

I did the integration and I got the right answer. But the question remains, the specific heat capacity at constant pressure; C_p should be used at constant pressure. Here, the pressure is changing? A qualitative expalnation would suffice. Thanks
 
The pressure isn't changing; there's no process occurring. c_P is just a variable.
 

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