Question

Describe what is meant by a dynamic equilibrium in terms of the vapor pressure of a liquid.

Short answer

Dynamic equilibrium in terms of the vapor pressure of a liquid is a state where the rates of evaporation and condensation are equal, resulting in a constant vapor pressure. This constant vapor pressure represents the balance between the forces driving evaporation and those driving condensation, and depends on the temperature and the chemical nature of the substance. In a closed system containing a liquid, some molecules at the surface will escape into the vapor phase (evaporation), while others will collide with the liquid surface and re-enter the liquid phase (condensation). When these rates become equal, a state of dynamic equilibrium is reached.

Step-by-step solution

Define Dynamic Equilibrium

Dynamic equilibrium is a state in which the rates of the forward and reverse reactions in a system are equal. This results in a constant concentration of reactants and products, even though individual molecules may be changing. #Step 2: Define Vapor Pressure#

Define Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phase (liquid or solid). It depends on the temperature and the chemical nature of the substance. In the case of a liquid, it means the pressure exerted by the molecules that have escaped from the surface of the liquid to form a vapor above the liquid. #Step 3: Explain Dynamic Equilibrium in terms of Vapor Pressure#

Explain Dynamic Equilibrium in terms of Vapor Pressure

In a closed system containing a liquid, some molecules at the surface of the liquid will have enough energy to overcome the intermolecular forces holding them in the liquid phase, and they will escape into the vapor phase. This process is called evaporation. As the vapor concentration increases, the likelihood of vapor molecules colliding with the surface of the liquid and re-entering the liquid phase (called condensation) also increases. As the system evolves, the rates of evaporation and condensation will eventually become equal, and a state of dynamic equilibrium is reached. At dynamic equilibrium, the vapor pressure remains constant, and the number of molecules evaporating from the liquid equals the number condensing back into it. This constant vapor pressure, which depends on the temperature and the chemical nature of the substance, represents the balance between the forces driving evaporation and those driving condensation.

Key concepts

Vapor Pressure

Vapor pressure is a fundamental concept in chemistry, especially when discussing the physical properties of liquids and solids. In a simple sense, it is the pressure created by the vapor above a liquid or solid as some of the molecules break free from the surface of the condensed phase into the gas phase. The more molecules that escape, the higher the vapor pressure.

Imagine a sealed container with just a liquid inside it. At first, some of the fastest-moving molecules at the surface of the liquid will have enough energy to escape into the airspace above, creating a vapor. As more molecules enter the vapor phase, the pressure they exert increases. This pressure, specific to the chemical at a given temperature, is what we refer to as vapor pressure.

Vapor pressure is related to the