Physics
posted by Jon .
Approximately how long does it take for an oxygen molecule to diffuse across the interior of a cell that is 230 ì m in diameter?

Without knowing the diffusion coefficient, I have no idea.
You might consider this a "random walk" problem. The product of mean free path and molecular velocity is approximately the diffusion coefficient, D.
The average distance randomly walked is, as I recall,
sqrt (pi*D*t)