# Thermodynamics help

1. Oct 11, 2004

### mikeee

Need help!!

Ok, I'm having problems with the following question:

A container is filled with an unknown gas. To heat 1 kg of the gas by one degree under the constant pressure one needs 907.8 J, while the same increase of temperature of the gas when the colume is kept constant, needs 648.4 J.

Determine what gas is in the container.

-- if you guys can help point me in the right direction i'd appreciated it!

Last edited: Oct 11, 2004
2. Oct 11, 2004

### Soveraign

Well let's see. The 907.8J is related to heat capacity at constant pressure and the 648.4J is related the heat capacity at constant volume. In your Thermo book, since this is a gas, you should see a relation for an ideal gas that states gamma = cp/cv. Depending on this ratio, you can calculate if the gas is monatomic, diatomic, etc... In my book, this is discussed right after Mayer's equation cp = cv + R. Now, there are multiple examples of real world monatomic and diatomic gases. I believe Helium and Argon follow the monatomic model reasonably well, whereas Nitrogen and Oxygen follow the diatomic model well.

Is this enough info to get you started?

3. Oct 11, 2004