Calculating osmotic pressure vant Hoffs law

a. The osmotic pressure of solution 1 (see Figure 1-3) can be calculated by van't Hoffs law, which states that osmotic pressure depends on the concentration of osmotically active particles. The concentration of particles is converted to pressure according to the following equation:

where:

it = osmotic pressure (mm Hg or atm) g = number of particles in solution (osm/mol) R = gas constant (0.082 L—atm/mol—K) T = absolute temperature (K) C = concentration (mol/L)

b. The osmotic pressure increases when the solute concentration increases. A solution of 1 M CaCl2 has a higher osmotic pressure than a solution of 1 M KC1 because the concentration of particles is higher.

c. The higher the osmotic pressure of a solution, the greater the water flow into it.

d. Two solutions having the same effective osmotic pressure are isotonic because no water flows across a semipermeable membrane separating them. If two solutions separated by a semipermeable membrane have different effective osmotic pressures, the solution with the higher effective osmotic pressure is hypertonic and the solution with the lower effective osmotic pressure is hypotonic. Water flows from the hypotonic to the hypertonic solution.

e. Colloid osmotic pressure, or oncotic pressure, is the osmotic pressure created by protein (e.g., plasma proteins).

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