# For a gas having molar mass M, express specific heat at constant pressure in terms of heat capacity ratio

For a gas having molar mass $$M$$, express specific heat at constant pressure in terms of heat capacity ratio.

My attempt:

using $$C_p - C_V = R$$ and

$$\dfrac{C_p}{C_V} = \gamma$$

$$C_p = \dfrac{R \gamma }{ \gamma - 1}$$

But answer is $$C_p = \dfrac{R \gamma }{ M(\gamma - 1)}$$

But from where this $$M$$ is coming from? Isn't specific heat independent of $$M$$?

• I agree with your answer. – Chet Miller Jul 15 '19 at 12:07
• The answer you've got $\left(C_p=\dfrac{\gamma R}{\gamma-1}\right)$ has the SI units $\dfrac{J}{mol\cdot K}$. The provided answer is in $\dfrac{J}{g\cdot K}$. – Eashaan Godbole Jul 15 '19 at 13:57