Question

What is the normality of `0.3 M` of `H_3PO_4`?

Answer 1

see below

Explanation:

Normality is a concentration that depends by the reaction that you do, then it can assume different valours, and IUPAC recommende don't use it.
In spite of this, generally `H_3PO_4` is considered an acid and its Normality is like the concentration of `H^+`ions if the compound is completely dissociated, hence it would be triple of molarity = 0,9 M
If you want titrate the acid you never titrate the third hydrogen atom but the first (with indicator orange Methyl) or the second (with indicator Phenolphtaleine) so in these reactions `H_3PO_4` normality would be respectively 0,3 N and 0,6 N