§7.3 Applications of Conductivity Measurement Chapter 7 Electrochemistry §7.3 Applications of Conductivity Measurement Main contents: Monitoring the purity of water Measurement of ionizability Determination of solubility product and ionic product Conductometric titration
/S·m-1 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 water Tap Distilled Deionized Pure /S·m-1 1 10-2 ~1 10-3 <1 10-4 5.478 10-6 Fabrication of VLSI Silicon wafer
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.
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.
The equation can be rearranged to Ostwald showed how one can measure the dissociation constant of an acid. Ostwald dilution law The equation can be rearranged to mc Linearization
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.
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.
6. Conductometric titration The conductance variation of a solution during titration can serve as a useful method to follow the course of the reaction. A B C A’ B’ C’ V / ml / S·m-1 endpoint 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
Homework Due time: Sep. 24