Question

Consider an experiment in which starch is dissolved in a liter of water. Some of the solution is placed into a securely tied dialysis bag. The dialysis bag is placed into a beaker containing distilled water and iodine for 30 minutes. What are the correct answers for the questions below? (Note: Iodine reacts with starch to create a black/purple color.) What would happen to the color of the solution in the bag? a. The solution in the bag would turn purple as the iodine reacts with the starch. b. The solution in the bag would grow lighter as the starch leaves the bag and enters distilled water and iodine.

Answer 1

Answer:

a. The solution in the bag would turn purple as the iodine reacts with the starch.

Explanation:

According to this question, a solution containing starch is placed into a securely tied dialysis bag. The dialysis bag is then placed into a breaker containing distilled water and iodine for 30mins.

The starch is a solute substance, which when added to the solution in the dialysis bag makes the solution in the bag HYPERTONIC in comparison to the hypotonic (low solute concentration) distilled water+iodine in the beaker. Based on this concentration gradient (difference in concentration), osmotic flow will occur across the dialysis bag (semi-permeable membrane).

Note that, osmosis is the movement of water from a region of low solute concentration to a region of high solute concentration across a membrane. Hence, water+iodine from the breaker will move into the solution in the dialysis bag.

Because the solution entering the dialysis bag contain iodine, it will react with the starch content of the dialysis bag and form a dark purple coloration inside the dialysis bag.