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Diprotic Acid quiz #1

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Terms in this set (10)

  • What is a diprotic acid?
    A diprotic acid is a compound that can donate two acidic hydrogen ions (H+) per molecule, typically represented by the general formula H2A.
  • What defines a diprotic acid?
    A diprotic acid is any acid that can donate two protons, such as H2SO4 (sulfuric acid) or H2CO3 (carbonic acid).
  • Is phosphoric acid a diprotic or triprotic acid?
    Phosphoric acid (H3PO4) is a triprotic acid because it can donate three acidic hydrogen ions.
  • What are the equilibrium expressions for the diprotic weak acid H2A?
    For H2A, the first dissociation (Ka1) is: Ka1 = [H3O+][HA−] / [H2A]. The second dissociation (Ka2) is: Ka2 = [H3O+][A2−] / [HA−].
  • Why is Ka1 always greater than Ka2 for a diprotic acid?
    Ka1 is always greater than Ka2 because it is easier to donate the first proton than the second, making the first dissociation much stronger than the second.
  • What are the three major forms of a diprotic acid as it loses protons?
    The three forms are H2A (acidic form), HA− (intermediate form), and A2− (basic form).
  • How are the acid and base dissociation constants of diprotic acids and bases related to Kw?
    Ka1 is connected to Kb2 and Ka2 is connected to Kb1; multiplying each pair gives Kw, which is 1.0 × 10⁻¹⁴ at 25°C.
  • What does it mean for the intermediate form of a diprotic acid to be amphoteric?
    The intermediate form (HA−) can act as either an acid or a base because it can both donate and accept a proton.
  • When calculating pH for a solution of H2A, which dissociation constant should you use?
    You should use Ka1, treating H2A as a monoprotic acid for the initial pH calculation.
  • Which equilibrium constant would you use if the intermediate form of a diprotic acid is accepting a proton?
    You would use Kb2 if the intermediate form is acting as a base and accepting a proton.