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

AI Thread Summary
To find the specific heat at constant pressure (Cp) for a gas with molar mass M, the relationship Cp/Cv = y is established. The initial attempt leads to the equation Cp = (Ry)/(y-1), but this does not match the expected answer of Cp = (Ry)/(M(y-1)). The discrepancy arises from not incorporating the molar mass M into the calculations correctly. The discussion emphasizes the importance of checking units and dimensions in the equations used. Clarification is sought on how to properly include M in the derivation to arrive at the correct expression for Cp.
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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



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

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

This isn't the answer though, the given answer is C_p=\frac{Ry}{M(y-1)}. Why? How does M come into the picture?
 
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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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