Diffusion problem

Paul

I am trying to calculate what to expect if I do the following experiment, but it seems a bit tricky (involving Fick's Laws?) - I put down a sample of ethanol in the middle of a large room, in a cyclindrical glass of diameter 5 cm. There is enough ethanol that the glass will not dry out during the experiment, the source is therefore continuous. Also, the room is large enough that the ethanol does not reach the edges during the experiment. Diffusion constant for ethanol in air is D. There is no airflow. Ethanol slowly moves outwards in a circle due to diffusion into the air. (Assume standard temp, pressure and humidity). After time 't' (seconds), at distance 'x' (cm) from the source, what is the concentration of ethanol in parts per million?

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