Diffusion

[sykosat2004]

Okay so we did this experiment where we had a glass tube with litmus papers at 3cm intervals. We put ammounium sulphate soaked cotton wool in one end. The time between each litmus paper turning blue progresiively got bigger each time. Can anyone explain why? cheers

[newtron]

The rate at which something travels due to diffusion is proportional to the concentration gradient (dC/dx, where C is concentration and x is the distance along the tube)according to fick's law. As the ammonium sulphate is transported by diffusion, the concentration across the tube decreases, and there for the rate at which the solute is moving also decreases. If this is homework, I suggest you look up Fick's law and try to get a better handle on it.

[newtron]

That was supposed to read "...the concentration gradient along the tube decreases."

[sykosat2004]

Nice answer thanks for that!