Question

TWO BEAKERS, ONE CONTAINING 0.010 M NACL(AQ) AND THE OTHER CONTAINING 0.010 M ALCL3(AQ) ARE PLACED INSIDE A BELL JAR AND SEALED. THE BEAKERS ARE LEFT UNTIL THE WATER VAPOR HAS COME TO EQUILIBRIUM WITH ANY LIQUID IN THE CONTAINER. THE LEVELS OF THE LIQUID IN EACH BEAKER AT THE BEGINNING OF THE EXPERIMENT ARE THE SAME, AS PICTURED BELOW. DRAW THE LEVELS OF THE LIQUID IN EACH BEAKER AFTER EQUILIBRIUM HAS BEEN REACHED. EXPLAIN YOUR REASONING.

Answer 1

First we write the dissociation reactions for both electrolytes:

The water vapor that has come to equilibrium with the liquids in both beakers is called the vapor pressure. Vapor pressure descends as the number of electrolytes in the aqueous solution increases. In this case NaCl produces 2x[NaCl] number of particles, that is 0.02 mol of particles. In the case of AlCl₃ it produces 4x[AlCl₃], that is 0.04 mol of particles. Given that they start at the same volume, the vapor pressure in the NaCl beaker should be higher, so the volume should be lower.