This lab experiment investigates the physical and chemical characteristics of the iron-ammonia complex, giving information on transition metal ion coordination chemistry. A stable complex with a dark brown colour is created using iron(III) chloride hexahydrate and concentrated ammonia solution, offering a greater understanding of the role of ligands in complex compound synthesis and their importance in generating novel materials and catalysts.
This experiment will help students understand the coordination chemistry of transition metal ions and the role of ligands in forming complex compounds.
Materials
This experiment requires iron(III) chloride hexahydrate, concentrated ammonia solution, distilled water, and ethanol. Other laboratory supplies will be required, such as beakers, test tubes, a hot plate, a magnetic stirrer, and a centrifuge.
Methods for Preparing Iron-Ammonia Complex
The experiment will begin with the preparation of a 0.1 M solution of iron(III) chloride hexahydrate in distilled water. The solution will then be introduced in small amounts to a test tube containing concentrated ammonia solution. On a hot plate, the mixture will be heated and agitated with a magnetic stirrer until a dark brown precipitate appears. The precipitate will then be centrifuged from the solution and washed with ethanol to eliminate any contaminants.
Related Experiment: The Heat of Solution of Ammonium Nitrate Experiment
Expected Observation of the Results
The creation of a dark brown precipitate, which is the iron-ammonia complex, is the predicted result of the reaction. The presence of the iron ion and the ligand ammonia causes the complex’s hue. Because of the coordination connection established between the iron ion and the ammonia ligand, the complex will be stable in solution.
Reasons for Some Results
The complex’s dark brown hue is caused by the iron ion’s d-d transition. When the complex is formed, the electrons in the iron ion’s d-orbitals are excited to higher energy levels, resulting in visible light absorption. The absorbed light correlates to the complex’s hue, which in this example is a dark brown.
The Color of the Products
As already mentioned, the color of the iron-ammonia complex is caused by the iron ion’s d-d transition. The complex absorbs light in the visible spectrum, resulting in a dark brown appearance.
Equation of the Reaction
The equation of the reaction for the formation of the iron-ammonia complex is as follows:
FeCl3.6H2O + 6NH3 → [Fe(NH3)6]Cl3 + 6H2O
Specific Significance of the Experiment
The iron complex is stable in solution due to the coordinate bonding formed between the iron ion and the ammonia ligand. This experiment also underlines the importance of ligands in the synthesis of complex molecules, as well as the role they play in the physical and chemical properties of the complex.
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