Electrons and Quantum Mechanics - Oakland Schools

Equipment
pH paper
small test tubes
eyedroppers
Safety Concerns
Avoid skin contact with all the solutions; concentrations used in this experiment may
cause irritation. Goggles must be worn throughout the experiment.
Sources
http://web.archive.org/web/20050210092308/www.woodrow.org/teachers/chemistry/in
stitutes/1986/exp35.html
Procedure
1. Prepare the following cation test solutions: 1.0 M CuSO 4 (dissolve 250 g
CuSO 4·5H 2 O in sufficient distilled or deionized water to make 1.0 L of solution),
0.10 M NiSO 4 (dissolve 28.1 g of NiSO 4·7H 2 O in sufficient distilled or deionized
water to make 1.0 L of solution), and 0.10 M CoSO 4 (dissolve 28.1 g CoSO 4·7H 2 O
in sufficient water to make 1.0 L of solution).
2. Prepare saturated solutions of tartaric acid and of oxalic acid.
3. Adjust the pH of the solutions prepared in step 2 so that they are neutral to pH
paper by adding small amounts of ammonia solution.
4. Prepare a 1% solution of dimethylglyoxime in ethyl alcohol solution.
5. Measure l ml of the copper(II) solution into 11 small test tubes. Repeat with the
cobalt(II) and nickel(II) solutions.
6. Set aside a test tube of each metallic cation as a control.
7. Add several drops of each ligand solution or a small scoop of a solid ligand to
each of the remaining 10 test tubes containing the copper(II) ion. Mix the
contents of each tube thoroughly after each addition. Repeat for the cobalt and
nickel solutions. Observe carefully as the ligands are added. Continue to add
ligand until a noticeable color change occurs. If no color change has been
observed after an excess of ligand (approx. 3 mL) has been added, record no
visible change on the data chart. Always compare the sample with the control.
Note: Some of the complexes may have several intermediate states in which the
color may vary; therefore, be sure to add an excess of ligand after the initial
color change.
8. Line up the resulting complexes for each cation in order of the spectrum
(ROYGBIV).
9. Record observed color changes in a data table similar to the one following.
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