diffusion and molecular weight

Question

I had to do an experiment for biology class. I had to put a drop of red dye on a Petri dish that had corn syrup spread on it and then I had to do the same with just blue dye. I had to determine which dye would diffuse faster and how it makes sense in regards to the molecular weight of the dye. A lower molecular weight should yield a faster diffusion rate, the red was lower but it diffused at a slower rate than the blue. I want to know if this makes sense. 

Answer 1

In general, it does not make sense, because as you stated, a lower molecular wt compound should diffuse faster than a higher molecular wt compound. Assuming the temperature is constant, it might be that the blue dye was present at a significantly higher concentration then the red dye. Diffusion rate will be affected by the concentration gradient according to Fick’s first law of diffusion.