  We calculate the phase diagrams for a harmonically trapped ideal gas mixture
of fermionic atoms and bosonic molecules in chemical and thermal equilibrium,
where the internal energy of the molecules can be adjusted relative to that of
the atoms by use of a tunable Feshbach resonance. We plot the molecule fraction
and the fraction of Bose-condensed molecules as functions of the temperature
and internal molecular energy. We show the paths traversed in the phase
diagrams when the molecular energy is varied either suddenly or adiabatically.
Our model calculation helps to interpret the {\it{adiabatic}} phase diagrams
obtained in recent experiments on the BEC-BCS crossover, in which the
condensate fraction is plotted as a function of the {\it{initial}} temperature
of the Fermi gas measured before a sweep of the magnetic field through the
resonance region.
