Tasks
- Prepare Dialysis for 30:1 Colloid vs CaCl2
- Prepare iodide ion selective electrodes
- Prepare 10 mL 3 M NaCl
- Place electrode in 15 mL falcon tube with enough NaCl solution to match volume in electrode
- cover and store upright until needed
- Prepare 50 mL 4 M KNO3
- Add KNO3 to outer double junction cell, filling narrow tube + ~ 0.5 inches further
- Place electrode in small vial with enough KNO3 solution to cover the vycor tip
- Prepare 50 mL 0.01 M KI + 0.1 M KNO3
- Cut a short piece (~ 3 in) of silver wire
- Place in KI/KNO3 solution
- Electrolyze the solution using the power supply
- The standard reduction potential for Ag/AgI is -0.15 V
- Oxidation occurs at the anode, which is connected to the red lead
- Electrolyze at low power (low current) until the wire appears coated
- Test your electrodes with a range of KI solutions
- The Ag/AgCl electrode slides inside of the KNO3 bridge solution (this is a double junction electrode)
- The Ag/AgI wire can be connected directly to a multimeter using alligator clips
- You will continue to connect your Ag wire to the red lead on the multimeter
Ki concentrations (mM)
|
Voltage (mV)
|
ln[I-]
|
50 |
-278 |
3.912023005
|
25 |
-247.4 |
3.218875825
|
10 |
-237 |
2.302585093
|
5 |
-217.4 |
1.609437912
|
2 |
-198.3 |
0.693147181
|
- Prepare new KI Stock Solution (the previous KI solutions were discarded because there was an error with the dilutions that were prepared)
- 50 mM KI (0.83 g KI in 100 mL H2), which through dilution:
- 25 mL 25 mM KI
- 25 mL 10 mM KI
- 25 mL 5 mM KI
- 25 mL 2 mM KI
- 10 mM NH4SCN (0.7612 g NH4SCN in 1 L H2)
- 75 mM AgNO3 (0.637 g AgNO3 in 50 mL H2)
|