Chapter 13, Problem 58A

Interpretation Introduction

Interpretation: Evaporation process, vapor process, and boiling point are to be described.

Concept introduction:

A liquid is a nearly incompressible fluid and has the shape of its container and maintains a (almost) constant volume under all conditions of pressure. The volume is fixed if the temperature and pressure are both constant.

Answer to Problem 58A

Because the rate of evaporation and condensation occur continuously and at the same rates

Explanation of Solution

A dynamic equilibrium between the liquid and vapor forms when evaporation occurs in a closed container because the vapor molecules are unable to leave.

When a reaction is reversible, a dynamic equilibrium occurs. Since substances shift from reactants to products at identical rates, there is no net change. The formation of reactants and products occurs so quickly that neither of their concentrations changes.

Thus, in dynamic equilibrium at the molecular level, the rate at which the liquid evaporates is the same as the rate at which the vapor condenses. The equilibrium is called dynamic because both condensation and evaporation occur at the same rate.