Question

when brown iodine is exposed to starch, it turns dark purple. in an experiment, you placed a cornstarch solution in a small bag made of dialysis tubing. next, you placed the bag in a beaker of water containing ten (10) drops of iodine. if the solution in the dialysis tubing bag turned dark purple (select all that apply)
the cornstarch moved into the beaker.
the bag was selectively permeable.
the iodine moved into the bag.
the bag was permeable to iodine.
the bag was permeable to cornstarch.

Explanation:

Dialysis tubing is a selectively permeable membrane. Starch is a large - sized molecule and cannot pass through the dialysis tubing. Iodine is a small - sized molecule. Since the solution in the dialysis tubing (which has starch) turned dark purple (a positive test for iodine - starch reaction), it means that iodine molecules moved from the beaker (where they were initially) into the dialysis tubing bag. Also, the fact that iodine could pass through while starch could not indicates that the bag (dialysis tubing) is selectively permeable. And if iodine could pass through, it means the bag is permeable to iodine.

Answer:

• the bag was selectively permeable.
• the iodine moved into the bag.
• the bag was permeable to iodine.