Potassium dichromate is a bright orange chemical compound used in various applications. It is a strong oxidizing agent and can be toxic if ingested or inhaled.
| IUPAC Name | Potassium dichromate |
| Molecular Formula | K2Cr2O7 |
| CAS Number | 7778-50-9 |
| Synonyms | Potassium bichromate, Potassium chromate(VI), Bichromate of potash |
| InChI | InChI=1S/2Cr.2K.7O/q;;2*+1;;;;;;;;/h;;2*;7*1- |
Potassium Dichromate Properties
Potassium Dichromate Formula
The formula of potassium bichromate is K2Cr2O7. It consists of two potassium atoms (K), two chromium atoms (Cr), and seven oxygen atoms (O). Each potassium atom has a +1 charge, while each chromium atom has a +6 charge. The presence of two chromium atoms in the formula indicates the compound’s dimeric structure.
Potassium Dichromate Molar Mass
The molar mass of potassium bichromate is calculated by adding up the atomic masses of its constituent elements. Potassium has a molar mass of 39.10 grams per mole (g/mol), chromium has a molar mass of 52.00 g/mol, and oxygen has a molar mass of 16.00 g/mol. Therefore, the molar mass of potassium bichromate is 294.18 g/mol.
Potassium Dichromate Boiling Point
Potassium bichromate does not have a specific boiling point, as it decomposes before reaching a boiling point. However, when heated, it undergoes thermal decomposition, releasing toxic fumes of chromium oxide and oxygen.
Potassium Dichromate Melting Point
The melting point of potassium bichromate is approximately 398 degrees Celsius (°C) or 748 degrees Fahrenheit (°F). At this temperature, the solid crystals of potassium bichromate transform into a liquid state.
Potassium Dichromate Density g/mL
The density of potassium bichromate is about 2.68 grams per milliliter (g/mL). This indicates that a given volume of potassium bichromate is relatively heavier compared to an equal volume of water.
Potassium Dichromate Molecular Weight
The molecular weight of potassium bichromate is the same as its molar mass, which is 294.18 grams per mole (g/mol). It represents the combined mass of all the atoms present in one molecule of the compound.
Potassium Dichromate Structure
Potassium bichromate has a dimeric structure, meaning it consists of two chromium atoms bonded to each other through oxygen atoms. The potassium atoms are also bonded to the oxygen atoms, creating a complex network of atoms in the compound.
Potassium Dichromate Solubility
Potassium bichromate is highly soluble in water. It readily dissolves in water to form an orange solution. The solubility of potassium bichromate increases with temperature. However, it has limited solubility in organic solvents.
| Appearance | Bright orange crystals |
| Specific Gravity | 2.68 g/mL |
| Color | Orange |
| Odor | Odorless |
| Molar Mass | 294.18 g/mol |
| Density | 2.68 g/mL |
| Melting Point | 398 °C (748 °F) |
| Boiling Point | Decomposes |
| Flash Point | Not applicable |
| Water Solubility | Highly soluble |
| Solubility | Soluble in water, limited in organic solvents |
| Vapor Pressure | Negligible |
| Vapor Density | Not available |
| pKa | Not applicable |
| pH | Acidic (around pH 4) |
Potassium Dichromate Safety and Hazards
Potassium bichromate poses significant safety hazards. It is highly toxic if ingested, inhaled, or comes into contact with the skin. The compound is a strong oxidizing agent, which can react violently with combustible materials, increasing the risk of fire. Exposure to potassium bichromate can cause severe skin irritation, burns, and allergic reactions. Inhalation of its fumes or dust can lead to respiratory issues and lung damage. Long-term exposure is associated with adverse health effects, including chromate-induced lung cancer. It is crucial to handle potassium bichromate with extreme care, wearing appropriate protective equipment and ensuring proper ventilation to minimize the risks to health and safety.
| Hazard Symbols | Corrosive, Health hazard, Acute toxic |
| Safety Description | – Highly toxic – Corrosive – Causes burns |
| UN IDs | UN 3086 (Class 6.1) |
| HS Code | 2841.10.10 |
| Hazard Class | 6.1 (Toxic substances) |
| Packing Group | III |
| Toxicity | Acute oral toxicity: Highly toxic<br>Chronic toxicity: Carcinogenic potential |
Note: The hazard symbols used in the table are commonly recognized international symbols. It’s important to refer to specific regulations and safety guidelines for comprehensive information on the handling and storage of potassium bichromate.
Potassium Dichromate Synthesis Methods
Several methods can synthesize potassium bichromate. One commonly used method involves the reaction between potassium chromate (K2CrO4) and chromic acid (H2CrO4). The reaction proceeds in an acidic medium, typically with sulfuric acid (H2SO4) as a catalyst. The reaction can summarize it.
2K2CrO4 + 2H2CrO4 + 2H2SO4 → K2Cr2O7 + Cr2(SO4)3 + 4H2O
Another method involves the oxidation of potassium chromate using a strong oxidizing agent, such as concentrated sulfuric acid (H2SO4), and a reducing agent, such as ethanol (C2H5OH). The reaction can summarize it.
2K2CrO4 + H2SO4 + 3C2H5OH → K2Cr2O7 + Cr2(SO4)3 + 7H2O + 3CO2
Potassium hydroxide (KOH) reacts with chromium trioxide (CrO3) in an aqueous medium to produce potassium bichromate. In an aqueous medium, the reaction takes place. The reaction can summarize it.
2KOH + CrO3 → K2Cr2O7 + H2O
These synthesis methods require appropriate safety precautions due to the toxic and corrosive nature of the reagents involved. It is important to perform these reactions in a well-ventilated area, wear protective equipment, and handle the chemicals with care. Additionally, adherence to proper waste disposal protocols is essential to minimize environmental impact.
Potassium Dichromate Uses
Potassium bichromate finds applications in various fields due to its unique properties. Here are some of its common uses:
- Oxidizing agent: Chemical reactions widely employ potassium bichromate as a strong oxidizing agent to oxidize alcohols into aldehydes or ketones.
- Laboratory reagent: Analytical chemistry utilizes potassium bichromate as a reagent for tests and experiments, including determining organic compounds and conducting redox reactions.
- Tanning industry: The leather industry utilizes potassium bichromate as a tanning agent to process animal hides and convert them into durable leather products.
- Photography: Black-and-white photography incorporates potassium bichromate into developing solutions and uses it to sensitize emulsions for specific photographic effects.
- Wood preservation: To protect wood against decay, fungi, and insect attack, the wood preservation industry utilizes potassium bichromate as a highly toxic wood preservative.
- Manufacturing of pigments: Potassium bichromate plays a vital role in producing pigments such as chrome yellow and chrome orange, which industries utilize in paints, inks, and dyes.
- Electroplating: Electroplating processes utilize potassium bichromate to provide a decorative and corrosion-resistant coating on metals, including zinc, aluminum, and brass.
- Pyrotechnics: Potassium bichromate plays an essential role in pyrotechnic mixtures, contributing vibrant orange colors to fireworks and flares.
- Textile industry: The dyeing and printing of textiles incorporate potassium bichromate to achieve desired colors and enhance color fastness.
- Calibration of laboratory glassware: For accurate volume measurements, potassium bichromate solutions serve the purpose of calibrating laboratory glassware.
These diverse applications highlight the versatility and significance of potassium bichromate in various industries and scientific endeavors.
Questions:
Q: What is the correct formula for potassium dichromate?
A: The correct formula for potassium bichromate is K2Cr2O7.
Q: What is potassium dichromate?
A: Potassium bichromate is a chemical compound that is bright orange in color and is commonly used as an oxidizing agent.
Q: Is potassium dichromate ionic or covalent?
A: Potassium bichromate is an ionic compound.
Q: What is the minimum amount of water needed to dissolve 3 mol of potassium dichromate?
A: The minimum amount of water needed to dissolve 3 mol of potassium bichromate is approximately 564 grams.
Q: What is the molar mass of potassium dichromate?
A: The molar mass of potassium bichromate is 294.18 grams per mole (g/mol).
Q: Potassium dichromate MSDS?
A: Material Safety Data Sheets (MSDS) for potassium bichromate provide detailed information about its hazards, handling, storage, and first aid measures. Please refer to reliable sources or manufacturers for the specific MSDS.
Q: How is potassium dichromate prepared from chromite ore?
A: Potassium bichromate can be prepared from chromite ore by roasting it with potassium hydroxide or potassium carbonate and subsequently isolating the product.
Q: How many grams of potassium dichromate were added to the volumetric flask?
A: The exact number of grams of potassium bichromate added to the volumetric flask would depend on the desired concentration and volume of the solution.
Q: How would you distinguish between propanal and propanone using acidified potassium dichromate?
A: Propanal would be oxidized to propanoic acid by acidified potassium bichromate, while propanone (acetone) would not show any reaction.
Q: Is potassium dichromate a reducing agent?
A: No, potassium bichromate is an oxidizing agent.
Q: How to write the potassium dichromate formula?
A: The potassium bichromate formula is written as K2Cr2O7.