Ammonium Dichromate

Ammonium dichromate is a brilliant orange-colored crystalline solid. It easily ignites and burns, leaving a large amount of green residue behind. However, if we begin heating it in a sealed container, the container may break due to the material’s decomposition. When coupled with or contaminated with combustible material, it can also operate as a potent oxidising agent. When placed in water, it dissolves. (NH4)2Cr2O7 is the molecular formula for ammonium dichromate. And the structure is depicted in the image below.

Properties:

The chemical exists in orange-colored acidic crystals that are soluble in water and alcohol at normal temperature and pressure. It is made by the action of chromic acid on ammonium hydroxide, followed by crystallisation. A single type of ammonium ion makes up the (NH4)2Cr2O7  crystal (C2/c, z=4) furthermore, at the symmetry C1 locations (2,3). Every NH4+ centre is irregularly surrounded by 8 oxygen atoms with N—O lengths ranging from 2.83 to 3.17 A, as is typical of hydrogen bonds.

Oxidation:

Ammonium dichromate is a strong oxidizing agent that reacts with any reducing agent, typically violently. The reaction becomes more intense as the reducing agent becomes stronger. It’s also been used to help alcohols and thiols oxidise faster. In the presence of Mg(HSO4)2 and moist SiO2, ammonium dichromate can be used as a highly efficient reagent for the oxidative coupling of thiols under solvent-free conditions. Under moderately mild circumstances, the reactions provide reasonable yields. In ZrCl4/wet SiO2 in solvent free circumstances, the chemical is also utilized to oxidize aliphatic alcohols to their corresponding aldehydes and ketones, with comparatively high yields.

Reactions:

The following exothermic reaction occurs when a pile of salt is ignited during the volcano demonstration:

 (NH4)2Cr2O7 (s) → Cr2O3 (s) + N2 (g) + 4 H2O (g)     (ΔH = −429.1 ± 3 kcal/mol)

It has the same thermodynamic instability as ammonium nitrate. Once we start the decomposition reaction, it will finish, creating a massive dark green powder of chromium (III) oxide.

In this process, not all of the ammonium dichromate decomposes. The remaining ammonium dichromate produces a yellow or orange colour solution when the dark green colour powder is mixed with water.

Ammonium dichromate formula:

Dichromate is a 2-charged ion that is employed as an oxidizer. Dichromate is a chemical compound that is utilised in a variety of processes. Because of its ionic characteristics, it may be converted into a variety of salts that can be employed in oxidation-reduction reactions.

The chromium oxidation number, i.e. The Cr content of (NH4)2Cr2O7 is +6.

(NH4)2Cr2O7 is the molecular formula for ammonium dichromate.

Ammonium dichromate Uses:

It has a variety of uses, including pyrotechnics and lithography in the early days of photography, as a source of pure nitrogen in chemistry labs, and as a catalyst. In addition, businesses employ it as a mordant in the dyeing of pigments, the production of alizarin, chrome alum, leather tanning, and oil purification.In the manufacture of the phosphor raster of TV screens, LCDs, and many other devices, photosensitive films containing PVA, ammonium dichromate, and a phosphor are spin-coated as liquid slurries. The ammonium dichromate, on the other hand, also serves as a photoactive site.                                   

Conclusion:

Orange-red needles of ammonium dichromate form during crystallisation. A hazardous chemical salt used to make organic emulsions like gelatin more susceptible to the hardening effects of actinic light. It is more light-sensitive.

Ammonium dichromate is an extremely dangerous and known carcinogen that is identical to all chromium (VI) compounds. Furthermore, it is a powerful irritant at the same time.