Chapter 15.3, Problem 30SSC

Interpretation Introduction

Interpretation:

The molar heat of condensation of ammonia for a given the molar heat of vaporization is to be determined.

Concept introduction:

Molar heat of condensation: The heat evolved when 1mol of vapor condenses.

Molar heat of vaporization: The heat evolved when 1mol of liquid vaporizes.

Answer to Problem 30SSC

The molar heat of condensation of a given substance is the exact opposite to molar heat of vaporization.

$\begin{array}{l}\Delta H_{condensation}=-\Delta H_{vaporization}\\ \therefore \Delta H_{condensation}=-23.3\raisebox{1ex}{$kJ$}\!\left/ \!\raisebox{-1ex}{$mol$}\right.\end{array}$

Explanation of Solution

The molar heat of condensation of a given substance is the exact opposite to molar heat of vaporization. Since, the molar heat of vaporization is already given; the molar heat of condensation will have same magnitude as the molar heat of vaporization but with a negative sign.

Conclusion

The molar heat of condensation of ammonia is -23.3kJ/mol.