@property<EOL><INDENT>def UNIFAC_Q(self):<DEDENT>
if self.UNIFAC_groups:<EOL><INDENT>return UNIFAC_RQ(self.UNIFAC_groups)[<NUM_LIT:1>]<EOL><DEDENT>return None<EOL>
r'''UNIFAC `Q` (normalized Van der Waals area), dimensionless.
        Used in the UNIFAC model.

        Examples
        --------
        >>> Chemical('decane').UNIFAC_Q
        6.016