Question

a) Beaker A contains 1-liter of pure water. If you add 2 mol of glucose into this beaker, then the osmolarity of the solution is 2 Osm in beaker A.

b) Beaker B contains 1-liter of pure water. If you add 1 mol of sodium chloride into this beaker, then the osmolarity of the solution is 2 Osm in beaker B.

c) If you then pour the contents of beaker A and beaker B into beaker C, the osmolarity of the solution is 2 Osm in beaker C.

These were fill-in-the-blank questions and the words in bold were the answers. Can you please explain why these are the correct answers? (especially the third one)

Answer 1

b) Sodium chloride dissociates into Na⁺ and Cl^- ions. Both sodium and chloride ions affect the osmotic pressure of the solution.Thus, for every 1 mole of NaCl in solution, there are 2 osmoles of solute particles (i.e., 1 mol/L NaCl solution is a 2 osmol/L NaCl solution).

c) Non-ionic compounds like glucose do not dissociate. Therefore 1 mol/L solution of glucose is 1 osmol/L and 2mol/L of glucose is 2osmol/L of glucose.

When you mix both the solutioin beaker A which has 2osm/L of glucose and beaker B 2osm/Lof Nacl into a beaker C, the Osm of that container will have 2osm/L concentration.

2osm/L (beaker C) = 2 moles of glucose + 1 moles of Nacl/L