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Buffer Solutions, Function

Buffer Solutions, Function. HCl is added to pure water. HCl is added to a solution of a weak acid H 2 PO 4 - and its conjugate base HPO 4 2-. Simplified >. HOAc + H 2 O H 3 O + + OAc -. HOAc H + + OAc -. Simplified >. The Metal Cation is not shown.

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Buffer Solutions, Function

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  1. Buffer Solutions, Function HCl is added to pure water. HCl is added to a solution of a weak acid H2PO4- and its conjugate base HPO42-.

  2. Simplified >

  3. HOAc + H2O H3O+ + OAc- HOAc H+ + OAc- Simplified > The Metal Cation is not shown OAc-: CH3COO-

  4. Preparing a Buffer You want to buffer a solution at pH = 4.30 or [H3O+] = 5.0 x 10-5 M POSSIBLE ACIDS Ka HSO4- / SO42- 1.2 x 10-2 HOAc / OAc- 1.8 x 10-5 HCN / CN- 4.0 x 10-10 Best choice is…? What are the pKas? What are the molarities of HA, A-?

  5. Use pH = pKa + log[A-] [HA] pH = 4.74 + log(0.1/0.1) = 4.74

  6. HOAc H+ + OAc-

  7. Acid-Base Titrations Adding NaOH from the buret to acetic acid in the flask, a weak acid. In the beginning the pH increases very slowly. Additional NaOH is added. pH rises as equivalence point is approached. Additional NaOH is added. pH increases and then levels off as NaOH is added beyond the equivalence point.

  8. Strong Acid Strong Base Reaction

  9. Titrations

  10. Indicators for Acid-Base Titrations

  11. Some Values of Ksp Table 18.2 and Appendix J

  12. PRECIPITATION REACTIONSSolubility of Precipitates Lead(II) iodide

  13. Lead(II) Chloride PbCl2(s) Pb2+(aq) + 2 Cl-(aq) Ksp = 1.9 x 10-5 = [Pb2+][Cl–]2

  14. Barium SulfateKsp = 1.1 x 10-10 (b) BaSO4 is opaque to x-rays. Drinking a BaSO4 cocktail enables a physician to exam the intestines. (a) BaSO4 is a common mineral, appearing a white powder or colorless crystals.

  15. Common Ion Effect PbCl2(s) Pb2+(aq) + 2 Cl-(aq) Ksp = 1.9 x 10-5

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