Question

the freezing point depression constants of the solvents cyclohexane and naphthalene are 20.1°C/m and 6.94°C/m respectively. Which would give a more accurate determination by freezing point depression of the molar mass of a substance that is soluble in either solvent? Why?

Answer 1

Explanation:

It'd be better to use cyclohexane.  The possible explanation is that the freezing temperature will change by 20.1 degrees for each mole of substance added to 1 kg of cyclohexane, although the same amount added to naphthalene will change its freezing point just by 6.94 degrees.

It is so much easier to identify a larger change more adequately than a smaller one.  You would actually not have a 1 molal solution in operation, so the variations in freezing points would be even smaller than the ones already described.