If a laboratory assistant prepared solutions of 0.8M, 0.6M, 0.4M, and 0.2M
sucrose but forgot to label them there would be no need for him to panic. Knowing the
principles of water movement through the processes of osmosis and diffusion, one can
conduct a rather simple experiment to determine which flask contains which solution.
According to the principles of osmosis, water typically moves from solutions of low solute
concentration to areas of high solute concentration. This information would allow one to
form the basis of his or her experiment in trying to determine the concentrations of the
unlabeled solutions. The specifics of the experiment will be discussed along with the
results one would expect from such an experiment. However, it is also important to know
why these predictable results would occur. They will also be discussed.
In conducting the experiment it would be necessary to obtain dialysis tubing. This
would play the role of the semi-permeable membrane. This is important because without a
semi-permeable membrane substances other than water, such as glucose, could exit the
apparatus and throw off the results. Diffusion of the solutes would occur. Diffusion is the
process of particles moving from an area of low concentration to an area of high
concentration. Next, the tubing would be filled with samples of the solutions from each
flask and tied off at both ends. Space would be left for expansion of the bag. The bags
would then be weighed and the masses would be recorded. In this particular experiment,
four bags would be made (taking solution from each of the four flasks). These four bags
would be placed in four separate beakers of distilled water. Each beaker would contain
the same amount of water. It would be very important to label which flask's solution each
bag contains. The bags of the unknown sucrose concentrations would be left in the
beakers for about a half hour then...