Find Specific Heat at Constant Pressure of Gas with Molar Mass M

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Homework Help Overview

The problem involves finding the specific heat at constant pressure (C_p) for a gas with a given molar mass (M) and relates the ratio of specific heats (C_p/C_v) to a variable (y). The original poster presents an equation derived from the ideal gas law and expresses confusion regarding the presence of molar mass in the provided answer.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to derive C_p using relationships from thermodynamics and the ideal gas law, but questions why their result differs from the expected answer involving molar mass. Other participants question the dimensional consistency of the proposed answer.

Discussion Status

The discussion is ongoing, with the original poster seeking clarification on their derivation and the role of molar mass. Some participants have pointed out potential issues with unit consistency, indicating a productive examination of the problem.

Contextual Notes

The original poster's confusion suggests a need for further exploration of the relationships between specific heats and molar mass, as well as the implications of dimensional analysis in thermodynamic equations.

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Homework Statement


For a gas of molar mass M, Cp/Cv=y. Find specific heat at constant pressure.



The Attempt at a Solution



[tex]C_p=\frac{Pdv}{ndt}+C_v[/tex]
PV=nRT,
P=constant
[tex]\frac{P}{n} \frac{dv}{dt}=R[/tex]

Substituting in the above equation:
[tex]C_p(\frac{y-1}{y})=R[/tex]
[tex]C_p=\frac{Ry}{y-1}[/tex]

This isn't the answer though, the given answer is [tex]C_p=\frac{Ry}{M(y-1)}[/tex]. Why? How does M come into the picture?
 
Physics news on Phys.org
Anybody? Please?
 
Have you checked your units ? Your proposed answer has the wrong dimensions.
 
Where have I made the mistake? What am I doing wrong?
 

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