Chapter 17.3, Problem 28LC

Interpretation Introduction

Interpretation: The comparison between the molar heat of fusion and the molar heat of solidification is to be drawn.

Concept introduction:

The molar enthalpy of fusion $\text{Δ}{H}_{fus}$ , is the amount of energy that must be added to 1 mole of a solid substance to transform into 1 mole of liquid at constant pressure.

The molar enthalpy of solidification $\Delta H_{solid}$ , is the amount of energy that must be removed from 1 mole of a liquid substance to transform into 1 mole of solid at constant pressure.

Answer to Problem 28LC

The molar enthalpy of solidification is exactly the same as the molar enthalpy of fusion.

Explanation of Solution

As fusion and solidification are opposite processes, heat absorbed in one is the same in magnitude as the heat released in the other. As in fusion, heat is absorbed, the molar enthalpy of fusion is positive, and in solidification, heat is released, and the molar enthalpy of fusion is negative with the same numerical value.