@property<EOL><INDENT>def alphag(self):<DEDENT>
kg, rhog, Cpg = self.kg, self.rhog, self.Cpg<EOL>if all([kg, rhog, Cpg]):<EOL><INDENT>return thermal_diffusivity(k=kg, rho=rhog, Cp=Cpg)<EOL><DEDENT>return None<EOL>
r'''Thermal diffusivity of the gas phase of the mixture if one exists
        at its current temperature and pressure, in units of [m^2/s].

        .. math::
            \alpha = \frac{k}{\rho Cp}

        Examples
        --------
        >>> Mixture(['ammonia'], ws=[1]).alphag
        1.6968517002221566e-05