STUDENT DIRECTIONS FOR EXPERIMENT 4 FERRIC THIOCYANATE PART A STOICHIOMETRY
1. Before coming to class, read the lab write-up pages 1 to 4 and Harris 529-531.
2. Before coming to lab, calculate how many mL of the 1.0 M HClO4, the 0.05 M KSCN, and the 0.05 M Fe(NO3)3 stock solutions to use for the preparation of the 1.0 x 10-3 M solutions of Fe3+ and SCN- in separate 100-mL volumetric flasks (page 3 of the write-up).
3. As soon as you come to class, listen to the audio-cassette tape "Formulas and Stability Constants of Metal Complexes" while reading the accompanying booklet.
4. Have the calculation in 2) above approved by an instructor and then prepare the two solutions. Take only the volumes of stock solutions needed.
5. Prepare the test solutions indicated on page 3.
6. Obtain decent clean 1-cm pathlength cells and an assignment to a spectrophotometer from the instructor and measure the absorbance of the nine Fe-SCN test solutions and the one Fe(III) stock solution.
7. Clean everything up when you are done.
8. Correct the absorbance readings for the blank if necessary. Plot the data and determine the stoichiometry for the complex.
STUDENT DIRECTIONS FOR EXPERIMENT 4 FERRIC THIOCYANATE COMPLEX PART B EQUILIBRIUM
1. Before coming to class, read page 1 and pages 4 to 12 of the lab write-up and from Harris, 97-101, 315-316 and 326-331.
2. Before coming to lab, calculate how many milliliters of the stock solutions (p. 9) to use in the preparation of 250 mL of your test solution.
3. Before coming to lab, work out how to do the calculations (p. 12) with a spreadsheet. (Even better, set up the spreadsheet for data entry during the lab.)
4. First thing in lab, listen to the audio-cassette tape while reading the accompanying booklet "Keq for the Fe3+ - SCN- Complex".
5. Have your solution preparation scheme in (2) approved by an instructor before using it. Make sure to use the perchloric acid salts (ClO4 -) for both the Fe2+ and the Fe3+ (do not confuse with solutions from part C.)
6. Make up your test solution, carry out the experiment, and start entering data into a spreadsheet (pp. 10-11).
7. Clean out the cell when you are done.
8. Continue with the spreadsheet analysis and plot the data. Perform a linear least squares analysis.
STUDENT DIRECTIONS FOR EXPERIMENT 4 FERRIC THIOCYANATE COMPLEX PART C FLASH PHOTOLYSIS KINETICS
1. Before coming to class, study page 1 and pages 13- 22 of the lab write-up.
2. Before coming to lab, calculate how you will make 50 mL each of the four solutions described on pp. 19-20.
3. The first thing when you come to class, listen to the audio-cassette tape "Ferric Thiocyanate Flash Kinetics", while reading the accompanying booklet.
4. Next, before preparing the test solutions, show your calculations from 2) to an instructor and have them approved.
5. Prepare the four solutions (p. 19), quantitatively. You can obtain a 25-mL graduated pipet from the instructor for measuring the 1 M HClO4 solution.
6. Calibrate your 100-µL Eppendorf pipet by weighing the water it dispenses.
7. Receive instruction on the use of the equipment.
8. Carry out the experiment (pp. 20-21).
9. Clean up the sample cell and around the flash photolysis apparatus.