Bromine (Br2) is a diatomic molecule composed of two bromine atoms. It is a reddish-brown liquid at room temperature and is highly reactive. It is used in various industries, including pharmaceuticals, agriculture, and water treatment.
| IUPAC Name | Bromine |
| Molecular Formula | Br2 |
| CAS Number | 7726-95-6 |
| Synonyms | Bromo, Molecular bromine, UN 1744, Diatomic bromine, Bromine-79, Bromine-81 |
| InChI | InChI=1S/Br2/c1-2 |
Bromine Properties
Bromine Formula
The chemical formula for bromine is Br2. This means that one molecule of bromine contains two bromine atoms. The formula is used to represent the composition of a substance, and it is essential in chemical reactions. The formula for bromine is used in various industries, including pharmaceuticals, water treatment, and agriculture.
Bromine Molar Mass
The molar mass of Br2 is 159.808 g/mol. This is the mass of one mole of Br2 molecules. Molar mass is an essential property in chemistry, as it helps determine the amount of substance needed for a given reaction. It is also used to convert between grams and moles of a substance.
Bromine Boiling Point
Br2 has a boiling point of 58.8 °C (137.8 °F). This is the temperature at which Br2 changes from a liquid to a gas. Br2’s low boiling point is due to its weak intermolecular forces, which allow the molecules to escape from the liquid state more easily. The high reactivity of Br2 makes it a dangerous substance to handle at high temperatures.
Bromine Melting Point
The melting point of Br2 is -7.2 °C (19.0 °F). This is the temperature at which solid Br2 changes into a liquid state. The low melting point of Br2 is due to its weak intermolecular forces, which allow the molecules to move more easily in the solid state. Br2 has the unique property of existing as a liquid at room temperature, which is rare among halogens.
Bromine Density g/mL
The density of Br2 is 3.12 g/mL. This means that one milliliter of Br2 has a mass of 3.12 grams. The high density of Br2 is due to its molecular weight and the close packing of its molecules in the liquid state. The high density of Br2 makes it useful in heavy organic synthesis reactions.
Bromine Molecular Weight
The molecular weight of Br2 is 79.90 g/mol. This is the sum of the atomic weights of the two Br atoms in the Br2 molecule. Molecular weight is an essential property in chemistry, as it helps determine the amount of substance needed for a given reaction.
Bromine Structure
Br2 is a diatomic molecule, meaning that it consists of two Br atoms bonded together. The two Br2 atoms share a pair of electrons, forming a covalent bond. The Br2 molecule has a linear structure, with the two Br atoms arranged in a straight line. The structure of Br2 is similar to other halogens such as chlorine and iodine.
| Appearance | Reddish-brown liquid |
| Specific Gravity | 3.12 g/mL |
| Color | Reddish-brown |
| Odor | Pungent, irritating odor |
| Molar Mass | 159.808 g/mol |
| Density | 3.12 g/mL |
| Melting Point | -7.2 °C (19.0 °F) |
| Boiling Point | 58.8 °C (137.8 °F) |
| Flash Point | Non-flammable |
| Water Solubility | 3.41 g/100 mL (25 °C) |
| Solubility | Soluble in chloroform, carbon tetrachloride, and ether |
| Vapour Pressure | 1.13 kPa at 25 °C |
| Vapour Density | 5.4 g/L |
| pKa | -5 |
| pH | Not applicable |
Bromine Safety and Hazards
Br2 is a hazardous chemical and should be handled with care. It is a corrosive liquid and can cause severe skin and eye irritation. Inhalation of Br2 vapors can lead to respiratory problems, and exposure to high levels can be fatal. Br2 is also a strong oxidizing agent and can react violently with flammable materials, causing fires or explosions. Proper protective equipment, such as gloves, goggles, and respirators, should always be worn when working with Br2. It should be stored in a cool, dry, and well-ventilated area away from heat sources and incompatible materials. In case of a spill or accident, immediately evacuate the area and follow proper clean-up procedures.
| Hazard Symbols | Skull and crossbones, Corrosive |
| Safety Description | Highly toxic, corrosive, and irritating to the skin, eyes, and respiratory system. |
| UN IDs | UN1744 |
| HS Code | 2801.30 |
| Hazard Class | 8 |
| Packing Group | II |
| Toxicity | LD50 (oral, rat) = 2 to 3 mg/kg |
Bromine Synthesis Methods
Various methods can synthesize Br2, depending on the desired purity and quantity.
One method involves the treatment of brine with chlorine gas in the presence of a catalyst such as iron. The resulting solution of sodium hypochlorite and sodium chloride is then acidified with hydrochloric acid, which liberates Br2 gas.
Another method involves the oxidation of hydrogen bromide gas with oxygen gas in the presence of a catalyst such as platinum or asbestos. Industries commonly use this method to produce high-purity Br2 for their applications.
Electrolysis extracts Br2 from brine by passing an electric current through the solution, which separates the sodium and chloride ions and produces Br2 gas as a byproduct.
Bromine Uses
Br2 has several important uses across various industries, including:
- Manufacturers use Br-based compounds as flame retardants in textiles, plastics, and electronic equipment to reduce the risk of fires by preventing the spread of flames.
- Pharmaceutical companies incorporate Br-based compounds in the production of various sedatives, tranquilizers, and analgesics.
- Water treatment plants use Br-based compounds as a disinfectant to effectively kill bacteria, viruses, and other harmful organisms.
- Pesticide and herbicide producers utilize Br-based compounds to control pests and weeds effectively.
- The oil and gas industry employs Br-based compounds in drilling operations to control corrosion and improve oil recovery.
- Producers use Br-based compounds in the production of photographic film and paper to effectively control the sensitivity and contrast of images.
- Chemical synthesis reactions use Br2 as a reagent to produce dyes, plastics, and pharmaceuticals.
Questions:
Q: Is Br2 polar or nonpolar?
A: Br2 is a nonpolar molecule because the two bromine atoms have the same electronegativity, resulting in an equal sharing of electrons in the covalent bond.
Q: Which compound most likely contains polar covalent bonds? NaCl, AlF3, Br2, NF3?
A: The compound that most likely contains polar covalent bonds is NF3 (nitrogen trifluoride), as the nitrogen and fluorine atoms have significantly different electronegativities, resulting in an unequal sharing of electrons in the covalent bond.
Q: What is ΔH0 for this reaction? Br2 (g) → Br2 (l), ΔHf° Br2 (g) = 30.91 kJ/mol
A: The ΔH0 for the reaction is -10.57 kJ/mol, as the heat of vaporization for Br2 is 41.48 kJ/mol and the heat of fusion is 30.91 kJ/mol (given in the question).
Q: Is Br2 a gas?
A: Br2 can exist in both gas and liquid states depending on the temperature and pressure conditions. At room temperature and standard pressure, Br2 is a reddish-brown liquid.
Q: What is bromine used for?
A: Bromine has several important uses across various industries, including flame retardants, water treatment, pharmaceuticals, pesticides, oil and gas industry, photography, and chemical synthesis.
Q: Is bromine a metal?
A: No, bromine is not a metal. It is a nonmetal element in the halogen group of the periodic table.