what is the n-factor for phosphoric acid?

n-factor of an acid is its basicity or the no. of H+ ions it produces on dissociation per molecule of acid. Generally, it equal to the no. of H+ ions present in the molecule but in some cases (organic acids like oxalic acid the no. of COOH is considered) it is different.

In Phosphoric acid (H3PO4) no. of H+ ions it produces on dissociation per molecule of acid is 3. Hence the n-factor for phosphoric acid H3PO4 is 3.