gas chemistry?

Question

why doesnt gas pressure depend on the type of gas?

Answer 1

To a certain extent it does depend on the type of gas. When we are using the ideal gas law, PV = nRT we are assuming that the molecules or atoms of the gas are negligible when compared to the volume of the container in which they are located and that there are no interactions between the molecules or atoms of the gas in the sample. If we use a more realistic equation, like the Van der Waals equation which has terms for size of the molecules in the gas and the interactions that they engage while in the gas, identity of the gas is important for the final pressure of the gas. In the ideal case, we discount those interactions, so everything fits neatly in PV = nRT, in which only the amount of the gas, the temperature and the volume in which it is contained determines the pressure of the gas. The ideal gas law fails at high pressures (molecules or atoms of gas are close to each other, so they are interacting and the volume is small, so their size matters) and at low temperatures (molecules are moving slower, so they do interact). So when you are doing a real gas pressure determination, you must find a real gas equation to model the behavior of the gas. The ideal gas law is what it says, ideal conditions, which in many real life applications are seldom encountered.

Answer 2

At the same temperature, all molecules have the same average kinetic energy. So the pressure of a gas is only dependent upon the number of them hitting the walls of the container per second. Now look up Avogadro's Law.