Osmosis on a Weekend

Here are some practice problems for osmosis. It may help to have a piece of paper and pencil as you do these just in case you need to draw or erase as you go along. I will provide the answer after each problem so you can check your work. Have fun and, as always, if you have questions, either ask questions here or in class. :)

1. Draw a circle and put .125M of halloween candy inside it. This will serve as the cell.
On the outside write .125 M of trick or treat bags. This will serve as the solution.

a. Are the halloween candy and trick or treat bags hyper, hypo, or isotonic to one another?
b. Will the halloween candy move? If so, which way?
c. Now, are the cell and solution hypo, hyper, or isotonic to each other?

ANSWER:
a. At the beginning, the halloween candy and the trick or treat bags are isotonic to each other because there is the same concentration of each on either side of the cell.
b. The halloween candy will move. It will move from the cell (high concentration of halloween candy) to the solution (trick or treat bag-low concentration)
c. Now, the cell is hypotonic and the trick or treat bag is hypertonic :)


2. If a cell is placed in a .25M solution, what happens to the cell? Will it shrink, burst, or remain the same?

ANSWER: If the cell is placed in a .25M solution, it means the solution is hypotonic and the cell is hypertonic (.75 M). If the solution is hypotonic, that means that there is less particles and a high concentration of water on the outside and more particles and less water on the inside. Because water will move high to low in the process of osmosis, the cell will expand and possibly even burst.

3. Draw a vertical line on your paper to act as the membrane. On the left side of the line write 2M KMnO4 and 1M H2SO4 and on the right side write 6M lactose and 8M galactose. Which side of the cell is hypotonic and which side is hypertonic or are both sides isotonic to one another?

ANSWER: KMnO4 and H2SO4 are ionic compounds so you have to work out the math in the following way:

KMnO4 (2M x 6 ions)= 12 M
H2SO4 (1M x 7 ions)= 7 M
Total: 19 M

The inside of the cell is hypertonic to the outside which is hypotonic.

4. A cell is placed in a .87M solution. What happens to the cell? Will it shrink, burst, or stay the same?

ANSWER: The cell is hypotonic because it is placed in a solution with a high concentration (.87M) of particles. This means that the cell has lots of water and the outside solution has very little. Osmosis is a process where water travels from high concentration to low concentration so the cell will shrink.


5. Draw a vertical line again to act as membrane. On the left side put .0125M of glucose, .125M of sucrose, and 1.25M of lactose. On the right side put .00125M of glucose, 12.5M of sucrose, 1.25M of lactose. Determine which way each solute will diffuse across the membrane.

ANSWER: The glucose will diffuse from left (.0125M) to right (.00125M) so the arrow should go -->, the sucrose will diffuse from right (12.5M) to left (.125 M) so the arrow should go <----, and lactose will move in both directions equally (both concentrations are 1.25 M).

I hope these 5 additional problems helped you. If you need more than this, let me know. Thanks and continue to have a good weekend! Dr. Rosin