Ammonium Dichromate: A Comprehensive Guide to its Formula, Preparation, Chemical Properties and more
Ammonium dichromate is an inorganic chemical compound with the formula (NH4)2Cr2O7. It is an orange-red crystalline solid, often used in pyrotechnics, and as a precursor to other chromium compounds. This article provides a comprehensive overview of ammonium dichromate, including its chemical formula, preparation method, physical and chemical properties, and applications.
Structural Formula
This is the structural formula of the ammonium dichromate:
Chemical Formula
The chemical formula of ammonium dichromate is (NH4)2Cr2O7. It consists of two ammonium cations (NH4+) and two dichromate anions (Cr2O7^2-). The molecule is held together by ionic bonds, formed between the positively charged ammonium ions and negatively charged dichromate ions.
Preparation Method of Ammonium Dichromate
Ammonium dichromate can be prepared by several methods, including the reaction of chromium trioxide with aqueous ammonia, and the reaction of ammonium chloride with potassium dichromate.
The following is the reaction of chromium trioxide with aqueous ammonia:
CrO3 + 6NH3 → (NH4)2Cr2O7
The reaction of ammonium chloride with potassium dichromate is as follows:
Physical Properties of Ammonium Dichromate
| Melting point | 180C |
| Boiling point | decomposes |
| Molecular weight | 252.07g/mol |
| Density | 2.115g/cm3 |
| Solubility in water | 18.2g/100mL |
| Solubility | Insoluble in acetoneSoluble in alcohol |
| Crystal structure | Monoclinic |
| Appearance | Orange red crystals |
Chemical Properties of Ammonium Dichromate
Ammonium dichromate is a powerful oxidizing agent and is highly reactive. It can ignite easily and burn with a green flame. It is soluble in water, producing a slightly acidic solution. When heated, it decomposes to form nitrogen, water, and chromium trioxide.
The following is the thermal decomposition reaction:
(NH4)2Cr2O7 → N2 + 2CrO3 + 4H2O
Applications of Ammonium Dichromate
Ammonium dichromate is commonly used as a reagent in organic synthesis, as a source of chromium ions in laboratory experiments, and as a component in pyrotechnic mixtures. It is also used in the preparation of chromium compounds, such as chromic acid, chromium nitrate, and chromium sulfate.
In photography, ammonium dichromate is used as a sensitizer in photolithography processes.
Conclusion
Ammonium dichromate is a highly reactive and versatile chemical compound with a range of applications in fields such as pyrotechnics, laboratory experiments, and photography. This article provides a comprehensive overview of the chemical formula, preparation method, physical and chemical properties, and applications of ammonium dichromate.
