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Chapter 7 Electrochemistry

Chapter 7 Electrochemistry. § 7.3 Applications of Conductivity Measurement. Main contents: Monitoring the purity of water Measurement of ionizability Determine solubility product and ionic product Conductometric titration. Silicon wafer. 1. Monitor the purity of water. Group works:

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Chapter 7 Electrochemistry

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  1. Chapter 7 Electrochemistry §7.3 Applications of Conductivity Measurement • Main contents: • Monitoring the purity of water • Measurement of ionizability • Determine solubility product and ionic product • Conductometric titration

  2. Silicon wafer 1. Monitor the purity of water Group works: Calculate the conductivity of pure water. at 25 oC, Kw = 10-14, [H+] = [OH] = 10-7 mol·dm-3 Fabrication of VLSI

  3. In-situ monitoring of the cleaning process : H2O2/H2SO4 DW rinse  dilute HF  SC-1 cleaning  DW rinse  hot DW rinse  DW rinse  SC-2 cleaning  DW rinse  dilute HF  DW rinse. DW - deionized water, SC-1: H2O2/NH3; SC – standard cleaning,SC-2: H2O2/HCl.

  4. 2. Measure the ionizability and dissociation constant c+ =c At infinite dilution Arrhenius suggested that the degree of dissociation of an electrolyte can be calculated using molar conductivity.

  5. mc Ostwald showed how one can measure the dissociation constant of an acid. Ostwald dilution law The equation can be rearranged to Linearization

  6. 3. Determine solubility and solubility products Example: The conductivity of a saturated AgCl solution is 1.86  10-4 S·m-1, while that for water is 6.0  10-6 S·m-1. Molar conductivity of AgCl is 0.01372 S·mol-1·m2. Calculate the solubility product for AgCl.

  7. 5. Determine ion product of water Water can be taken as a dilute solution of a strong electrolyte CH+ = COH- = Kw1/2 The specific conductance of highly purified water is 5.478 10-6 S·m-1. Calculate the concentration of hydrogen ion in water.

  8. A C / S·m-1 C’ B A’ B’ endpoint V / ml 6. Conductometric titration The conductance variation of a solution during titration can serve as a useful method to follow the course of the reaction. Ionic mobility of ions: Na+ + OH- + (HCl) = 5.19 20.52 Na+ + Cl- +(H+ + Cl-) 5.19 7.91 36.30 Precipitation reactions, neutralization reactions, and coordination reactions

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