If it is assumed that it is an ideal gas, then all of the molecules would have the same energy. Ideal gases are known to have "elastic collisions". This means that no energy is lost, gained, or transferred through collisions. If the gas is a real gas, then molecules within the contained oxygen would have different energy. Each molecule would have different velocities of how fast they are moving through a volume and collisions between one another would result in a transfer of energy between molecules.