Chromium trioxide, also known as chromic acid, is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid and is sometimes marketed under the same name.
| IUPAC Name | Chromium(VI) oxide |
| Molecular Formula | CrO3 |
| CAS Number | 1333-82-0 |
| Synonyms | Chromic anhydride, chromium oxide anhydride, trioxochromium Chromium(VI) oxide |
| InChI | InChI=1S/Cr.3O |
Chromium Trioxide Properties
Chromium Trioxide Formula
The formula of chromic anhydride is CrO3. It consists of one chromium atom bonded to three oxygen atoms.
Chromium Trioxide Molar Mass
The molar mass of chromic anhydride is calculated by adding the atomic masses of its constituent elements, which are chromium (Cr) and oxygen (O). The molar mass is approximately 99.994 g/mol.
Chromium Trioxide Boiling Point
Chromic anhydride does not have a distinct boiling point. Upon heating, it decomposes into chromium oxide and oxygen gas without going through a liquid phase.
Chromium Trioxide Melting Point
The melting point of chromic anhydride is around 196 °C. At this temperature, it transforms from a solid state to a liquid state.
Chromium Trioxide Density g/mL
The density of chromic anhydride is approximately 2.7 g/mL. This value represents the mass of the compound per unit volume.
Chromium Trioxide Molecular Weight
The molecular weight of chromic anhydride, also known as its molar mass, is about 99.994 g/mol. It is the sum of the atomic masses of chromium and oxygen atoms in the compound.
Chromium Trioxide Structure
Chromic anhydride has a molecular structure in which one chromium atom is centrally bonded to three oxygen atoms. It adopts a tetrahedral geometry, with the chromium atom at the center and the oxygen atoms at the corners.
Chromium Trioxide Solubility
Chromic anhydride is highly soluble in water. It readily dissolves, forming a solution of chromic acid. The solubility of chromic anhydride in water allows it to be used in various chemical processes and applications.
| Appearance | Dark red crystals |
| Specific Gravity | 2.7 g/mL |
| Color | Dark red |
| Odor | Odorless |
| Molar Mass | 99.994 g/mol |
| Density | 2.7 g/mL |
| Melting Point | 196 °C |
| Boiling Point | Decomposes |
| Flash Point | Not applicable |
| Water Solubility | Highly soluble |
| Solubility | Soluble in various solvents such as ethanol, ether etc |
| Vapor Pressure | Not applicable |
| Vapor Density | Not applicable |
| pKa | Not applicable |
| pH | Acidic (in solution) |
Chromium Trioxide Safety and Hazards
Chromic anhydride poses significant safety hazards and should be handled with care. It is a highly corrosive and oxidizing substance, capable of causing severe burns to the skin, eyes, and respiratory system. Inhalation or ingestion of chromic anhydride can lead to respiratory distress, gastrointestinal issues, and even organ damage.
Proper personal protective equipment (PPE) should be worn when working with chromic anhydride, including gloves, goggles, and a respirator. It should be stored in a cool, dry place away from incompatible materials and sources of ignition.
Disposal of chromic anhydride must be done in accordance with local regulations, as it is considered a hazardous waste. It should not be released into the environment.
| Hazard Symbols | Corrosive, Oxidizing |
| Safety Description | Avoid contact with skin, eyes, and inhalation. Use appropriate protective equipment. |
| UN IDs | UN 1463 |
| HS Code | 2819.90.90 |
| Hazard Class | 5.1 (Oxidizing agent) |
| Packing Group | II |
| Toxicity | Highly toxic |
Chromium Trioxide Synthesis Methods
There are several methods to synthesize chromic anhydride.
One common method involves the reaction between sodium dichromate and sulfuric acid. In a controlled environment, someone mixes sodium dichromate (Na2Cr2O7) with concentrated sulfuric acid (H2SO4). The reaction results in the formation of a deep red solution of chromic anhydride (CrO3) and sodium sulfate (Na2SO4) as a byproduct.
Another method involves the oxidation of chromium(III) compounds using strong oxidizing agents such as hydrogen peroxide (H2O2) or nitric acid (HNO3). In this process, mix the chromium(III) compound with the oxidizing agent under specific conditions to convert chromium(III) to chromic anhydride.
Prepare chromic anhydride by reacting chromium metal or chromium(II) compounds with powerful oxidizing agents such as potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7). The reaction leads to the formation of chromic anhydride.
It is important to note that the synthesis of chromic anhydride should be carried out with proper safety measures and in compliance with appropriate regulations. Experienced individuals must conduct the synthesis process in well-equipped laboratories to ensure their safety and minimize environmental impacts.
Chromium Trioxide Uses
Chromic anhydride finds application as an oxidizing agent in various chemical processes, including the production of organic compounds.
- Manufacturers use it to produce dyes and pigments, such as chrome yellow and chrome green.
- The electroplating industry employs it to deposit chromium on metal surfaces, offering corrosion resistance and an attractive finish.
- It finds use in the preparation of chromium catalysts for polymerization reactions in the production of plastics and synthetic materials.
- It plays a role in synthesizing pharmaceuticals and organic intermediates.
- Wood preservation treatments utilize it as a fungicide and insecticide to protect against decay and pests.
- Laboratories employ it as a reagent for various chemical tests and analyses.
- Utilizing it in the production of specialty glasses and ceramics enhances specific colors and properties.
- The tanning industry uses it to process leather, aiding in the stabilization and dyeing of hides.
- It is a component in the formulation of cleaning agents and surface treatments for metal surfaces.
It is important to handle chromic anhydride with caution due to its toxic and corrosive nature. Following proper safety protocols ensures the protection of individuals and the environment during its use and disposal.
Questions:
Q: What is CrO3?
A: CrO3 is chromic anhydride, a compound consisting of one chromium atom bonded to three oxygen atoms.
Q: Is CrO3 a strong oxidizing agent?
A: Yes, CrO3 is a strong oxidizing agent commonly used in chemical reactions to facilitate the oxidation of various compounds.
Q: What does CrO3 do to alcohol?
A: CrO3 can oxidize alcohols, converting them into corresponding carbonyl compounds, such as aldehydes or ketones.
Q: What organic product would you obtain from the reaction of 1-pentanol with CrO3, H2O, and H2SO4?
A: The reaction would yield the organic product 1-pentanone, which is a ketone.
Q: What is the best choice of reagent to perform the following transformation: PCC, HIO4, CrO3, NaOH?
A: The best choice of reagent for this transformation would be PCC (pyridinium chlorochromate).
Q: Is CrO3 amphoteric?
A: No, CrO3 is not amphoteric. It is a highly acidic compound but not capable of exhibiting basic properties.
Q: How to find the oxidation number of Cr in CrO3?
A: The oxidation number of Cr in CrO3 is +6.
Q: What is the name of CrO3?
A: The name of CrO3 is chromic anhydride.
Q: What does CrO3 do to nonanone alcohols?
A: CrO3 can oxidize nonanone alcohols, converting them into corresponding carbonyl compounds, such as nonanone ketones.
Q: What is the charge on the transition metal cation in CrO3?
A: The transition metal cation in CrO3, which is chromium, has a charge of +6.