# How to calculate n factor for salts in this reaction?

My source says : For salts which react such that no atom undergoes change in oxidation state , n-factor for such salt is the total moles of cationic /anionic species replaced in 1 mole of the salt .

For Example $$\ce{Na3PO4 + BaCl2 -> NaCl + Ba3(PO4)3}$$

N factor of $$\ce { Na3PO4}$$ is 3.

Please can anybody give more examples and explain that to me ?