Ap Biology Lab - Diffusion And Osmosis Worksheet (Page 2 of 5) in pdf

Ap Biology Lab - Diffusion And Osmosis Worksheet Page 2

4. A dialysis bag is filled with distilled water and then placed in a sucrose solution. The

bag's initial mass is 20 g, and its final mass is 18 g. Calculate the percent change of

mass, showing your calculations.

5. Did your results match your predictions? Propose an explanation for why your results

(either overall or an individual bag) may have differed from what you were expecting.

Assigned Solution

Determine the temperature of the room. ________

Table 3: Potato Mass in Various Solutions

Potato

Mass

% Change in

% Change

Initial Mass (g)

Final Mass (g)

Pieces

Difference (g)

Mass

Class Average

Distilled

Water

0.2 M

0.4 M

0.8 M

1.0 M

Graph the results for both your individual data and class average on graph paper.

Graph the results for Sucrose Molarity vs. % Change in Mass. The independent variable

is on the X-axis, and the dependent variable is on the Y-axis

6. Determine the molar concentration of the potato pieces. This would be the sucrose

molarity in which the mass of the potato does not change. To find this, draw the line

on your graph that best fits your data. The point at which this line crosses the x axis

represents the molar concentration of sucrose with a water potential that is equal to the

potato tissue water potential. At this concentration, there is no net gain or loss of water

from the tissue.

What is the molar concentration in which the mass of the potato does not change?

7. Calculate the solute potential ( Ψ ) for the sucrose solution using the formula below.

i = ionization constant (for sucrose, this is 1 because sucrose

Show your work! ___________

does not ionize in water)

C = molar sucrose concentration at equilibrium (determined

from graph)

Solute Potential Formula Ψ = -iCRT

R = pressure constant (0.0831 liter bar/mole °K )

T = temperature °K (273 + °C )

Ap Biology Lab - Diffusion And Osmosis Worksheet Page 2