Simple derivation of equilibrium conditions

Here is a simpler, less formal derivation of the three equiUbrium conditions in a multiphase 

It is intuitively obvious that, unless there are special constraints (such as internal partitions), an equilibrium state must have thermal and mechanical equiUbrium. A temperature difference between two phases would cause a spontaneous transfer of heat from the warmer to the cooler phase a pressure difference would cause spontaneous flow of matter. 

Thermodynamics and Chemistry, second e6Hion,version 3 20 by Howard DeVoe. Latest version www.chem.umd.edu/themobook 

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