Meaning of diprotic acid is that , it can loose two hydronium ions (H+) . For finding how many H+ ions it can give , we have to see its structure. Here it have only two hydroxyl groups that is -OH groups, and the hydrogen atoms joined to these only are ionisable. So only these
Tag: ions
sulfuric acid ionizes to give us hydronium ion and sulfate ion. H2SO4 (aq) → 2H+ + SO4