Question

Effect of Molecular weight on Diffusion Time (Minutes) 0 10 20 30 40 50 60 Percent increase Methylene Blue 14.022.0125.0 20.0 20.-22 -100 9.0|14.0/16.0 18.0 /19.0/19.000122.221 Potassium Permanganate According to your data, what molecule (methylene blue or potassium permanganate) diffused the fastest? Check Your Understanding 1.1 Based on the data, what generalization can be made about the relationship between diffusion rate and molecular weight? 1.2 By observing the rate of diffusion from the data collected, does diffusion rate change over time? If yes, does the rate increase or decrease? 1.3 Why does the rate of diffusion slow down or stop completely? 1.4 If your actual data did not match the expected results, what are the possible sources of error that could have occurred to give you inaccurate results? Curtu 8 Just Passing Through Understanding Diffusion and Osmosis 81 113

Answer 1

Methylene blue diffuses the fastest

1.1   The molecular weight and diffusion rate are inversely proprtional.

        That means lighter the molecular weight,faster the diffusion.

1.2   Yes ,the diffusion rate change over time.the rate of diffusion is faster until the equilibrium is reached.

1.3 The rate of diffussion slows down or stops completely ,when the concentrations of the substance on either side of the barrier become equal.

1.4 The rate of diffusion is affected by some facors like -concentration gradient,membrane permeability,temperature , pressure.

The expected result may vary if any of these factors change during the process of diffusion.

1.5   If the temperature is increased it increase the energy and therefore the movement of molecules also increase.this results in the increase in rate of diffusion..

1.6    temperature is a measure of kinetic energy.Diffusion is affected by this kinetic energy.when we decrease the temperature ,the molecular speed decreases accordingly and therefore the rate of diffusion also decreases.

1.7     If more liquified agar is added, the density of solvent increases.therefore the rate of diffusion decreases.