Vapor pressure change The Kelvin equation

In Chapter 2.5.3.1, we considered water vapor as a gaseous constituent of air. Here, we discuss the vapor droplet equilibrium in clouds. We can consider each liquid as a condensed gas. At each temperature a part of the liquid-water molecule transfers back to the surrounding air, consuming energy (enthalpy of evaporation). The droplet is in equilibrium with air, when the flux of condensation is equal to the flux of evaporation. The equivalent vapor pressure p (in a closed volume or close to the droplet surface) is the vapor pressure equilibrium. In a closed system, it corresponds to the saturation vapor pressure. The vapor pressure equilibrium depends neither on the amount of liquid nor vapor but only on temperature and droplet size. 

Condensation and evaporation oeeurs at any vapor pressure. When the vapor pressure becomes smaller than the equilibrium value, the droplets are thermodynamically instable and evaporate. In equilibrium in both phases exists the same ehemieal potential  

From this we derive the molar evaporation enthalpy at temperature T (AyHI T = AvS )  

In laboratory praxis, from the Clausius-Clapeyron plot of In/ against 1/r, the enthalpy can be derived. 

In air, we have to consider droplets and not a bulk solution. From experience, we know that dispersed small droplets combine to larger drops. That is because the 

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