1. The problem statement, all variables and given/known data I dont know how to approach this problem, any help would be appreciated. i have a pipe 1 meter in lenght and 4mm in diameter. it containts 2 gases, D2 and He-3. each half of the pipe contains the 2gases and they are both at 400psi. how long does it take the gases to diffuse across the pipe completely? thanks. 2. Relevant equations ive looked into grahms law of diffusion but that doesnt seem to be helpful at all in this situation since it give me a proportional rate b/w two different molecules of gas 3. The attempt at a solution as far as ive gotten is finding the volumes of gas in each half of the pipe... not very far.