Q13.87P - Chemistry: Molecular Nature Of Matter And Change

Question

Question: The freezing point depression constants of the solvents cyclohexane and naphthalene are 20.1°C/m and 6.94°C/m, respectively. Which solvent would give a more accurate result if you are using freezing point depression to determine the molar mass of a substance that is soluble in either one? Why?

 

Step-by-Step Solution

Answer

Answer

Cyclohexane would give a more accurate result in this case because it has larger value of freezing point depression constant

Step 1: Definition

 

The freezing point depression says that the freezing point of a mixture of two components is lower than that of individual components is lower than that of individual components. It involves a solvent and a solute which you’ll mix with the solvent.

Step 2: Freezing point depression

 

To determine the molar mass of an unknown solute by freezing point depression you would select a solvent with as large a molal freezing g point depression constant as possible. 

The K_f for cyclohexane is roughly 4 times than the$6.94°C/m$  for naphthalene. It means their freeing point would have a major difference. Large freezing point depression constant makes it easier to observe the temperature change and determine molar mass.