# Specific heat.

1. Apr 25, 2007

### chaoseverlasting

1. The problem statement, all variables and given/known data
For a gas of molar mass M, Cp/Cv=y. Find specific heat at constant pressure.

3. 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 isnt the answer though, the given answer is $$C_p=\frac{Ry}{M(y-1)}$$. Why? How does M come into the picture?

2. Apr 26, 2007

### chaoseverlasting

3. Apr 26, 2007

### Mentz114

Have you checked your units ? Your proposed answer has the wrong dimensions.

4. Apr 27, 2007

### chaoseverlasting

Where have I made the mistake? What am I doing wrong?