Experiment 9 Lab report
1. Ken McFarland “Ion-selective Electrodes”, CHEM 1130, TA - Nastaran Marzijarani,
Section 108, Room 1871, Will Brubacher, Thursday 2:00 pm
2. Purpose of Experiment: This experiment is to find the concentration of an ion in a solution
through the sure of an ion selective electrode.
3. Procedure:
First create four reference solutions to calibrate the ISE. This should be done by serial
dilution from a single stock solution. Don’t forget to add 2 mL of ionic strength adjuster for
every 100 mL of sample. After all of the reference solutions are made, they should be tested
in order from the least concentrated to the most concentrated. The solution must be stirred
while the reading is being taken. Make sure that you don’t hit the electrode, and that it is not
removed from the solution. After you7 are done with the last solution, put the electrode into
distilled water to soak. Make a graph of the potentials vs. the log of the solution
concentration. This should be linear, if it is not consult with your instructor.
Measure the potentials for all of the samples your group has. Don’t forget to add the correct
ionic strength adjuster to each of them. The electrode should be soaked in distilled water
between solutions, just like it was at the end of the calibration. The same procedure should be
followed for these solutions as for the reference solutions.
4. Observations, Results and Data Sheets: See attached data sheets.
5. Questions:
1. The graph is a straight line from data point one to data point 4 on our graph. Both of
the outlying data points were slightly to high to fix exactly with the inner data points.
2. The concentration of our unknown was between 0.001M and 0.0001M. It did fall
within the linearity range of our graph. If it had not, the calculated concentration of our
unknown would be too high.
3. All of the samples should be of the same ionic strength, due to the addition of the ionic
strength adjuster. However, according to our data plot, the 1M and 0.00001M solutions
are of a slightly different ionic strength than the four solutions.