Solving for pH with diprotic/triprotic acids

  1. i know if you have an acid, say .0001 M HCl, to get the pH you simply take the -log of the acid concentration (which is the same as [H+]), but what if you have a diprotic (H2SO4) or triprotic (H3PO4) you need to multiply the acid contentration by 2 or 3 to get the new H+ concentration BEFORE plugging it into -log[H+]?

    and the same goes for pOH? eg. Mg(OH)2 needs to be multiplied by 2?
  2. jcsd
  3. siddharth

    siddharth 1,197
    Homework Helper
    Gold Member

  4. Mg(OH)2 do not completely ionise in water as do for instance NaOH or KOH.
  5. Borek

    Staff: Mentor

    Last edited by a moderator: Aug 13, 2013
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