Question

A semipermeable membrane separates two aqueous solutions at 37 °C. For each scenario, determine the solution into which a net flow of water, if any, will occur. Net flow is toward solution A Net flow is toward solution B No net flow Answer Bank solution A: 5.0% (w/v) glucose solution solution A: 0.20 M KCl solution solution A: 1.0 mM KCl solution solution B: 10.0% (w/v ) glucose solution solution B: pure water solution B: 1.0 mM NaCl solution solution A: 0.10 M KCl solution solution B: 0.10M CaCl, solution

Answer 1

Semipermeable membrane(SPM): It allows only solvent particles to pass through it.

Directon of flow of solvent particles(In aqueous solution solvent is water)

Solvent particles flow from lower concentration to higher concentration solution.

CASE 1

Solution A :5.0% (w/v) Glucose solution

Solution B: 10.0%(w/v) Glucose solution

Since 5.0% (w/v) Glucose is lower concentration solution hence direction of flow of solvent particles is  from A to B.

CASE 2:

Solution A: 0.20 M KCl solution

Solution B: Pure water

Since pure water has no solute hence it is at lower concentration hence water flows from pure water(Solution B) to 0.20M KCl solution (Solution A)

CASE 3:

Solution A: 1.0mM KCl solution

Solution B:1.0mM NaCl solution

Both solutions have same concentration hence there is no net flow of water.

CASE 4:

Solution A: 0.10M KCl solution

Solution B: 0.10M CaCl₂ solution

Osmotic concentration Of solution A is .10M ×2 =.20M

(Osmotic concentration is equal to number of ions × Molarity)

KCl gives two ions K⁺ and Cl^-

CaCl₂ solution has one Ca²⁺ and two Cl^- ions (Total 3)

Thus osmotic concentration is 3 × 0.10 M = .30M

Since water flows from lower osmotic concentration to higher concentration thus direction is from A to B.