Question

The following questions ask students to become familiar with key concepts in osmolarity.

1. A semipermeabile membrane which allows water to flow across but not ions or large molecules such as glucose, separates two solutions. An investigator examines the relationship between changes in osmotic concentration and the osmotic pressure differences across the membrane.

First, write out the formula for osmotic pressure, labeling the various parameters and indicating the units that each would have.

The investigator sets the osmolarity with glucose to be 300 mosm on the left (side A) and then alters the osmolarity of the solution on the right (side B) to values of 300 mosm, 600 mosm, 1200 mosm, and 2400 mosm. Calculate the pressure difference, in atmospheres and in mm Hg, between two solutions under these conditions

Now plot the pressure difference between the two solutions as a function of the change in osmolarity on a graph; be sure to label the axes

2. Two solutions are separated by a water permeable membrane that will not allow the movement of salts. The solution on the left (side A) has a concentration of 50 mM NaCl; the other solution on the right (side B) has a concentration of 500 mM NaCl. Calculate the osmolarity of both solutions.

Now calculate the difference in osmotic pressure that exists between the two components. Express this value both in atmospheres and in mm mercury

Which way would water flow?

****explanation also please****

Answer 1

2.

1 NaCl will give 2 ions in solution

50 mM NaCl will give 50 mM x 2 = 100 mM NaCl ions = C₁ (osmolarity) 0.1 osm

similarly 500 mM NaCl = 500 mM x 2 = 1000 mM NaCl ions = C₂ (osmolarity) = 1 osm

now calculating pressure difference

π₂ - π₁ = (1-0.1) R x T = 22 atm

1 atm = 760 mm mercury

22 atm = 16726.45 mm Hg

Sorry I forgot to calculate in mm Hg in picture please do it yourself

by using above conversion

thanks!

need more help comment back