Answer
See answer below.
Work Step by Step
Any reaction involving the ions $Ba^{2+}$ and $PO_4^{3-}$ would be satisfactory, for example the following acid base reaction:
$3\ Ba(OH)_2(aq)+2\ H_3PO_4(aq)\rightarrow Ba_3(PO_4)_2(s)+6\ H_2O(l)$
(Mixing barium hydroxide and phosphoric acid).
