Lab#: 8

Date: January 30, 2012

Topic: Ligand Exchange in the First Row Transition Metals Ions

Introduction: In this experiment you will investigate ligand exchange reactions

involving Cu2+ ions.

Apparatus: Anhydrous copper (II) sulphate, concentrated hydrochloric acid, concentrated ammonia solution, distilled water, test tubes, droppers and spatula.

Procedure: 1. A spatula is used to place a small amount of anhydrous copper (II) sulphate in a test tube.

2. 10 drops of distilled water is added to the anhydrous copper (II) sulphate, shake and record all observations.

3. To the test tube in step 2, concentrated ammonia solution was added drop by drop while shaking the test tube until there is no further change. Record all observations.

4. Steps 1&2 were repeated.

5. To the test tube from step 4, concentrated hydrochloric acid was added drop by drop while shaking until there is no further change. All observations were recorded.

Observation:

When water was added to the anhydrous copper (II) sulphate the following observations were recorded:

1. The solid anhydrous copper (II) sulphate converted to the copper (II) sulphate solution

2. There was a colour change of pale blue to dark blue.3. A gas was given off and the test tube became heated.

When Hydrochloric acid was added to the copper (II) sulphate solution there was a colour change from dark blue to green and a pungent gas was given off.

Discussion:

1. A ligand is a species that can donate one lone pair of electrons; this allows a ligand to form complexes with transition metals.

2. A ligand is a species that can donate one lone pair of electrons; this allows a ligand to form complexes with transition metals. The ligand would donate the appropriate amount of lone pair electrons to the transition metal thus forming the complex.

3. Ligand exchange states that when a ligand is added to a complex, if the ligand is stronger than the ligand is stronger than the one in the complex it will be displaced, as what occurred in the experiment.

4. During the experiment the following complexes were formed Tetra aqua copper (II) ions, Tetra chloro copper (II) ions and Tetra ammin copper (II) ions.

5. The chloride and ammonium ion were able to displace the H2O in the complexes formed due to the laws of ligand exchange, which states that if the ligand added to the complex is stronger than the one in the complex it will displace the weak ligand.

6.