When it conforms to all assumptions of kinetic theory
Nitrogen gas is not an ideal gas. It is a good choice for the study of ideal gas behavior due to it's Boyle temperature, the temperature at which a non-ideal gas exhibits ideal behavior, being near...
Yes, hydrogen gas is an ideal gas.
Strictly speaking no, as an ideal gas is simply a theoretical device. Though it can be treated as an ideal gas to an extent.
Nitrogen