Gibbs energy or chemical potential of a real gas

Molar Gibbs energy or chemical potential of a real gas 

Another way of defining a gas is to express a characteristic fiinctioa The most common example chosen is molar Gibbs energy, in the case of a pure gas, often interchangeable with chemical potential. Here we are focusing on the choice of variables P and T, and we aim to determine the chemical potential (or molar Gibbs eneigy) of the pure gas from the state equation written in the form  

So the volume is the first derivative of Gibbs energy with regard to pressure (at a constant temperature)  

If tends towards zero, we know that the gas tends towards the behaviour of a perfect gas, thus affecting the exponent the variables relative to the perfect gas, it becomes  

Often it is sufficient to choose, for the reference pressure, the pressure of 1 bar, which is low enough. 

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