Consider separate 1.0-l gaseous samples of h2, xe, cl2, and o2 all at stp. a. rank the gases in order of increasing average kinetic energy. b. rank the gases in order of increasing average velocity. c. how can separate 1.0-l samples of o2 and h2 each have the same average velocity?

1) I think all the gases have the same kinetic energy. Since kinetic energy depends only on temperature and since all are at STP. Kinetic energy is the energy possessed by a body or molecules in motion, for gases the kinetic energy increases with increase in temperature due to increased vibration of gas molecules.

2) Kinetic energy is given by the formula 1/2mv^2, where m is the mass and v is the velocity. All the gases have the same kinetic energy, mass and velocity are inversely proportional. Therefore, the most massive molecules will have the lowest average speed. H2 is the fastest, Xe is the slowest.
Xe, Cl2, O2, H2, in the order of increasing speed. 

3) Two separate gases will have the same kinetic energy at the same temperature, but not the same average speeds. To have the same average speed the two gases will not be at the same temperature.