Answer to Question #170462 in General Chemistry for Amlya Pouliot

Question

A 1.24M solution of sodium propionate (NaCH3CH2COO) with a density of 1.15 g/mL has an osmotic pressure of 48.5 atm at 16oC. Determine the van’t Hoff factor and the freezing point of the solution. Explain why the van’t Hoff factor is smaller than for an ideal solution.

Answer 1

Vant off , i=$Measured/ calculated$

=1.15/1.24

=0.93

At a given instant a small percentage of the ions are paired and count as a single particle. Ion pairing occurs to some extent in all electrolyte solutions. This causes the measured Van 't Hoff factor to be less than that predicted in an ideal solution.