Equilibrium 1

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The following figure shows the situation of liquid-vapor equlibrio for a given compound at a given temperature.

 

 

If the volume of the vapor phase becomes twice as big, which of the following figures better represents the system once the equilibrium is restored at the same temperature?

 

 

Wrong. The camera has doubled but the number of molecules in the vapor phase not.
Wrong. The volume of the vapor phase has doubled but the number of molecules is the same. That means a vapor pressure half that of the original sample while the temperature remains constant.
Wrong. The camera has doubled but the number of molecules in the vapor phase has increased more than twofold.
Correct. The camera has doubled and the number of molecules in the vapor phase has also doubled. The vapor pressure remains constant.

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