i did an experiment involving gas diffusion through a glass tube. HCl was on one side of the tube, while NH3 was on the other side. it took about 5 minutes for the gases to meet in the middle of the tube and form a precipitate. but the mean velociries of the HCL and NH3 gas molecules at 25 degrees celsius are around 500 m/s. why did it take so long for the molecules to meet and react?