Editing Acid (section)

==== Equivalence points ====
Due to the successive dissociation processes, there are two equivalence points in the titration curve of a diprotic acid.<ref>{{Cite web|title = Titration of Diprotic Acid|url = http://dwb.unl.edu/calculators/activities/diproticacid.html|website = dwb.unl.edu |access-date = 2016-01-24|archive-url = https://web.archive.org/web/20160207011433/http://dwb.unl.edu/calculators/activities/diproticacid.html|archive-date = 7 February 2016|url-status = dead}}</ref> The first equivalence point occurs when all first hydrogen ions from the first ionization are titrated.<ref name = learning>{{Cite book|title = Chemistry & Chemical Reactivity |url = https://books.google.com/books?id=i1g8AwAAQBAJ|publisher = Cengage Learning|date = 2014-01-24|isbn = 9781305176461|language = en|first1 = John C.|last1 = Kotz|first2 = Paul M.|last2 = Treichel|first3 = John|last3 = Townsend|first4 = David|last4 = Treichel}}</ref> In other words, the amount of OH<sup>−</sup> added equals the original amount of H<sub>2</sub>A at the first equivalence point. The second equivalence point occurs when all hydrogen ions are titrated. Therefore, the amount of OH<sup>−</sup> added equals twice the amount of H<sub>2</sub>A at this time. For a weak diprotic acid titrated by a strong base, the second equivalence point must occur at pH above 7 due to the hydrolysis of the resulted salts in the solution.<ref name = learning/> At either equivalence point, adding a drop of base will cause the steepest rise of the pH value in the system.