Chapter 14, Problem 95IAE

Interpretation Introduction

Interpretation:

Mass percentage of palmitic acid in the stearic acid sample should be determined.

Concept introduction:

Freezing point depression of a solvent occurs due to the addition of nonvolatile solute. The amount that the freezing point is lowered is proportional to the mole fraction of the solute. In dilute solutions, solute mole fraction is equal to its molality. The freezing point depression can be determined by

$\Delta T_f=-K_f\times m$

$\Delta T_f$ - freezing point depression (⁰C)

$K_f$ - proportionality constant ( ⁰C mol-1 kg) (depends on melting point, enthalpy of fusion, molar mass of the solvent)

m − molality (mol/kg)