A pure sample of the solvent phenol has a freezing point of 40.85 C. A 0.414 molal solution of isopropyl alcohol in phenol was observed to have a freezing point of 38.02 C. What is the freezing point depression of this solution?
1 Answer
Freezing point depression is a colligative property of solutions. To be sure, its magnitude is directly proportional to the concentration of solute in solution. Consider,
where depression implies the direction of this change is negative.
Moreover, consider isopropyl alcohol,
It won't significantly dissociate enough in the phenol solvent to warrant
Hence,
The depression stated in the question is deviates from the theoretical depression. This may be due to systematic error regarding the thermometer, human error reading the thermometer at the right time when the phenol solution totally melted, or use of contaminated reagents if this was empirically obtained.
