If you had 6 moles of CaCl2 and 5 moles of Na3PO4, which of these would be the limiting and excess reactant

Na3PO4 is excess reactant, CaCl2 is limiting reactant.

Explanation:

3CaCl2 + 2Na3PO4 - --> Ca3 (PO4) 2 + 6NaCl

from reaction : 3 mol 2 mol

given: 6 mol 5 mol (X)

X = (6*2) / 3 = 4 mol Na3PO4

For 6 mol CaCl2 we need 4 mol Na3PO4, but we have 5 mol Na3PO4,

Na3PO4 is excess reactant, so CaCl2 is limiting reactant.