Final answer:
Two gases with the same concentration and rms speed, but different molecular masses, can have the same pressure because pressure depends on the average kinetic energy, which remains the same due to the same temperature and speed.
Step-by-step explanation:
If two gases in different containers have the same concentration and same rms speed but the mass of a molecule of the first gas is twice the mass of a molecule of the second gas, their pressures can still be the same. According to the kinetic theory of gases, the pressure exerted by a gas in a container is directly proportional to the average kinetic energy of the molecules. Since kinetic energy depends on both mass and the square of the velocity, and assuming ideal gases, both gases will have the same average kinetic energy due to the same temperature.
For kinetic energy (KE) of gas molecules, KE = 1/2 mv^2, where m is mass and v is velocity. If the masses are different but the rms speeds are the same, both samples would still have the same kinetic energy because v2 remains the same and the difference in mass is offset by the rms speed. Since pressure is related to the kinetic energy of the gas particles (given by P = 2/3 (KE)), the pressure of both containers would be the same.