quiz 8 (3/5)

• polyprotic equilibrium expressions:

  diprotic-

  • Ka1- [H+][HA-]/[H2A]
  • Ka2- [H+][A --]/[HA-]

  triprotic:

  • Ka1- [H+][H2A-]/[H3A]
  • Ka2- [H+][HA--]/[H2A-]
  • Ka3- [H+][A---]/[HA--]
• calculations:

  when polyprotic acid + salts added to solution:

  • no neutralization = use pKa's to solve

  when polyprotic acid is titrated with SB:

  • find prominent compound type and use their formula

  di- H2A <-> HA- <-> A--

  WA | pKa1 | amphi. | pKa2 | WB

  WA= pH~4 | buffer=pH~pKa1 | pH=avg pKa | buffer=pH~pKa2 | WB=pH~9

  (KaCa)^1/2 | Ka1(Ca/Cb) | 1/2(pKa1+pKa2) | Ka2(Ca/Cb) | (KbCb)^1/2
• famous polyprotic acid equilibria:

  texas built on limestone:

  • H2O + CO2 <-> H2CO3 (Kp) [gas]
  • H2CO3 <-> H+ + HCO3 (Ka1) [acid]
  • HCO3 <-> H+ + CO3-- (Ka2) [acid]
  • CaCO3 <-> Ca++ + CO3- (Ksp)[solubility]

  acid rain from sulfuric acid:

  • H2O + SO3 <-> H2SO4 (Kp)
  • H2SO4 <-> H+ + HSO4- (Ka1 = infinit)
  • HSO4- <-> H+ + SO4- (Ka2 = 10^-2)