Question

Which of the following gases is an example of an ideal gas

Hydrogen

Helium

Oxygen

Nitrogen

None of these

Answer 1

All above gases at certain condition behave as an ideal gas but helium is most behave like ideal gas .

A fundamental assumption of the ideal gas law is that the individual particles of the gas do not interact. That is, there are no interparticle forces, nor do they collide. This implies infinitely small particles. Basically, any gas at a low enough pressure and high enough temperature will behave very close to an ideal gas. For example, nitrogen (N2) at STP is a close approximation to an ideal gas. Helium at STP is an even better approximation, but still not perfect. In fact, no real physical gas behaves exactly as an ideal gas.

Any gas will deviate from the ideal gas law if 1) the pressure is increased, or 2) the temperature is lowered. The pressure, or temperature at which deviation from ideal gas law behavior depends on the particles of the gas. Nitrogen (N2), a small, neutral, low polarizability molecule and has very low intermolecular forces. This gives N2 a very low boiling point (about 77 Kelvins). At atmospheric pressure, you'll have to lower its temperature to close to it's boiling point before you see significant deviation from the gas law. However, if the pressure is increased, say to 100 or 1000 atm., N2 will deviate from ideal gas law behavior even at room temperature.

In a similar way, Helium will show the same behavior. Helium, however, is a very small particle (noble gas = atoms not molecules), is extremely non-polarizable, and has very low inter-atomic forces. This results in a very low boiling point, about 4 Kelvins. Thus, Helium will demonstrate ideal gas law behavior to temperatures much closer to its boiling point and to much higher pressures when compared to N2.