Question

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. (2) Now calculate the difference in osmotic pressure that exists between the two components. Express this value both in atmospheres and in mm mercury (4) Which way would water flow?

Answer 1

Answer:

(1)

Osmolarity (A) = Molarity x No. Of Dissociates

             = 50 x 10-3 x 2 = 100 x 10-3 = 0.1 Osmol.

Osmolarity (B) = 500 x 10-3 x 2 = 1000 x 10-3 = 1 Osmol.

(2) (3)

Osmotic Pressure = Π = nRT/V = MRT

At room temperature (25C)

Osmotic Pressure (A) = 50 x 10-3 x 0.08206 x 298.15 = 1.2233 atm = 929.707 mmHg

Osmotic Pressure (B) = 500 x 10-3 x 0.08206 x 298.15 = 12.233 atm = 9297.078 mmHg

Difference = B-A = 9297.078 - 929.707 = 8367.371 mmHg = 11.0097 atm

(4) Water will flow from Side A to Side B (Dilute to Concentrated)