How to calculate n factor for salts in this reaction?
$$\ce{2 Na3PO4 + 3 BaCl2 -&gt; 6 NaCl + Ba3(PO4)2}$$
Now this is clearly evident that dividing whole equation by 2 we get 1 mole of $\ce{Na3PO4}$ and at the right hand side 3 moles of $\ce{NaCl}.$ Therefore, 1 mole of phosphate ion is replaced by 3 moles of $\ce{Cl-}$ ion.
Hence $n\text{-factor} = 3.$
In reactions like this where there's no change in oxidation number, the $n\text{-factor}$ will always be the net positive charge in 1 molecule of that compound, in this case since there are 3 $\ce{Na}$ ions in sodium phosphate, the $n\text{-factor} = 3 × 1 = 3.$