Suppose a container is evacuated to leave just one molecule of a gas in it. Let v_α and v_rms represent the average speed and the rms speed of the gas.

Figure shows graphs of pressure vs density for an ideal gas at two temperatures T₁ and T₂.

The mean square speed of the molecules of a gas at absolute temperature T is proportional to

The rms speed of oxygen at room temperature is about 500 m/s. The rms speed of hydrogen at the same temperature is about

The pressure of a gas kept in an isothermal container is 200 kPa. If half the gas is removed from it, the pressure will be