[Q&A] May 29, 2017
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Question: What is vapor-liquid equilibrium? Answer: When a liquid substance is placed in a sealed container, the molecules that evaporate into the air collide with each other as well as with the container walls, causing some of those gas molecules to return to the liquid. At a certain temperature, when the number of molecules that evaporate from the liquid surface into the air is equal to the number of molecules that return from the air back to the liquid at the same time, a dynamic equilibrium is established between the liquid in the container and the vapor on its surface. This dynamic equilibrium is known as vapor-liquid phase equilibrium, or simply vapor-liquid equilibrium. http://bbs.hcbbs.com/static/image/hrline/4.gif HaiChuan Network’s special May Day event, “Remembering the Glorious Moments,” warmly invites your participation. http://bbs.hcbbs.com/thread-1774529-1-1.html (Source: HaiChuan Chemical Forum) Summary post for HaiChuan Network’s special May Day event, “Remembering the Glorious Moments.” http://bbs.hcbbs.com/thread-1774532-1-1.html (Source: HaiChuan Chemical Forum)
The gas-liquid dynamic equilibrium in the packed tower is maintained stably
Vapor-liquid equilibrium, also known as gas-liquid equilibrium. It is a closed system composed of a mixture of n components, with gas and liquid phases coexisting. At a certain temperature and pressure, when the two phases reach equilibrium, the chemical potentials of each component in the gas and liquid phases tend to be equal. It is more convenient to use fugacity: when the fugacity of component i in the gas phase and the liquid phase of a mixture is equal, it is called gas-liquid equilibrium.
When a liquid substance is placed in a sealed container, due to the collisions between molecules that evaporate into the air, as well as between the evaporated molecules and the container walls, some of those gas molecules return back to the liquid. At a certain temperature, when the number of molecules that evaporate from the liquid surface into the air is equal to the number of molecules that return from the air back to the liquid at the same time, a dynamic equilibrium is established between the liquid in the container and the vapor on its surface. This dynamic equilibrium is known as vapor-liquid phase equilibrium, or simply vapor-liquid equilibrium.
When a liquid substance is placed in a sealed container, collisions between the molecules that evaporate into the air, as well as between those evaporated molecules and the container walls, cause some of the gas molecules to return to the liquid. At a certain temperature, when the number of molecules that evaporate from the liquid surface into the air equals the number of molecules that return to the liquid, a dynamic equilibrium is established between the liquid inside the container and the vapor on its surface. This dynamic equilibrium is known as vapor-liquid equilibrium, or simply vapor-liquid balance.
When a liquid substance is placed in a sealed container, due to the collisions between molecules that evaporate into the air, as well as between the evaporated molecules and the container walls, some of those gas molecules return back to the liquid. At a certain temperature, when the number of molecules that evaporate from the liquid surface into the air is equal to the number of molecules that return from the air back to the liquid at the same time, a dynamic equilibrium is established between the liquid in the container and the vapor on its surface. This dynamic equilibrium is known as vapor-liquid phase equilibrium, or simply vapor-liquid equilibrium.
According to the concept of phase equilibrium, on each tray of a distillation column, when the high-temperature vapor phase comes into contact with the low-temperature liquid phase, heat and mass transfer occur. As a result, part of the high-temperature gas condenses and part of the low-temperature liquid vaporizes, increasing the concentration of light components in the vapor phase and the concentration of heavy components in the liquid phase. When the concentrations of the two phases reach a limit at which they no longer change, the temperature of the vapor phase on that tray equals the temperature of the liquid phase, and the vapor and liquid phases are in equilibrium.
The gas-phase condensation rate is the same as the liquid-phase evaporation rate!
Answer: When a liquid substance is placed in a sealed container, the molecules that evaporate into the air collide with each other as well as with the container walls, causing some of those gas molecules to return to the liquid. At a certain temperature, when the number of molecules that evaporate from the liquid surface into the air is equal to the number of molecules that return from the air back to the liquid at the same time, a dynamic equilibrium is established between the liquid in the container and the vapor on its surface. This dynamic equilibrium is known as vapor-liquid phase equilibrium, or simply vapor-liquid equilibrium.
The liquid phase no longer vaporizes, and the vapor phase no longer condenses
Several phases are formed from a mixture or solution; these phases coexist in a state of physical equilibrium