# Volume of gases

1. Oct 22, 2015

### Karan Punjabi

Ar STP Every gas occupies same volume of 22.4 L but how it can be because every gas molecule has different size right? So they should occupy different volumes right? If I'm wrong at any point then please correct me

2. Oct 22, 2015

### jbriggs444

In an ideal gas, the molecules are far apart. The size of molecules is a small fraction of the total volume. That is the assumption that goes into the 22.4 liters per mole approximation. In a diffuse gas, pressure is a function of the average kinetic energy of each molecule and the concentration of molecules. At STP and one mole per 22.4 liters, the average kinetic energy and the concentration of molecules is fixed and does not depend on molecular weight. Accordingly, the pressure is fixed and does not depend on molecular weight.

3. Oct 22, 2015

### Karan Punjabi

So that's just a approximation that volume is 22.4 L but in practical the volume vary little bit right ? I know that kinetic energy is fixed for any gas at a given constant temperature.

4. Oct 22, 2015

### jbriggs444

Right. Real gasses are not quite ideal.

5. Oct 22, 2015

### Karan Punjabi

Thank you so much this doubt was not letting me study for my exams.