@property<EOL><INDENT>def Zg(self):<DEDENT>
Vmg = self.Vmg<EOL>if Vmg:<EOL><INDENT>return Z(self.T, self.P, Vmg)<EOL><DEDENT>return None<EOL>
r'''Compressibility factor of the mixture in the gas phase at the
        current temperature, pressure, and composition, [dimensionless].

        Utilizes the object oriented interface and
        :obj:`thermo.volume.VolumeGasMixture` to perform the actual calculation
        of molar volume.

        Examples
        --------
        >>> Mixture(['hexane'], ws=[1], T=300, P=1E5).Zg
        0.9403859376888885