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Hypobromous Acid, also known as Bromanol or hydroxide bromine, is a weak and unstable acid that is in +1 oxidation state. Hypobromous acid has physical and chemical properties similar to hypohalites. Hypobromous acids have disinfectant properties i.e., the capacity to kill bacteria and pathogens and are hence used as Disinfectant, Oxidiser, Deodorant, and Bleach. It is called a weak acid because bromine is lightly associated with other elements in the compound and can therefore react quickly.
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Key Takeaways: Hypobromous Acid, Hypobromous Acid Formula, Hypobromite, HBrO formula, Formula
Hypobromous Acid
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Hypobromous acid, with the chemical formula HOBr and the bromine atom in the +1 oxidation state, is a weak, unstable acid. It can only be found in solution and has many of the same chemical and physical properties as hypochlorous acid (HClO). Hypobromous acid only partially dissociates into the hypobromite anion BrO and the cation H+ in aqueous solution. Hypobromite are the salts of Hypobromous acid. These salts, like the acid, are unstable and undergo a disproportionation reaction when evaporated or boiled to dryness, releasing the respective bromate and bromide salts.
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Hypobromous Acid Formula
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When bromine reacts with water Hypobromous acid is obtained as a result or yield product:
Br2 + H2O ⇔ HOBr + HBr
Hypobromous Acid Structure
Hypobromous Acid is HOBr having one electron of Hydrogen, has six electrons of Oxygen and has seven electrons of Bromine. One electron of hydrogen forms a pair with one electron of Oxygen and other one electron of Oxygen forms a pair with one of the electrons of bromide. After the pairing oxygen has four electrons unpaired and bromine has six electrons unpaired.
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Synthesis of Hypobromous Acid
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When Water is mixed with bromine, Hypobromous acid is obtained by the following reaction.
Br2 + H2O ⇔ HOBr + HBr
In Nature, bromoperoxidase, which are the enzymes that catalyse the oxidation of bromide along with hydrogen peroxide, leads to the formation of Hydrobromic acid. The reaction for the same is
Br- + H2O2 ⇔ HOBr + OH-
With a pKa of 8.65, Hypobromous acid is only partially dissociated in water at pH 7. Like acids, Hypobromite salts are unstable and they would undergo a gradual disproportionation reaction to produce bromate and bromide salts.
3BrO − (aq) → 2Br − (aq) + BrO − 3(aq)
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Chemical Properties of Hypobromous Acid
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Below table highlights the chemical properties of Hypobromous Acid.
| Chemical formula | HOBr or HOBr |
| Molecular weight | 96.911 g/mol |
| Density | 2.470 g/cm3 |
| Chemical names | Oxalyl bromide, bromic(I) acid, bromanol, hydroxide bromine |
| Acidity (pKa) | 8.65 |
| Boiling point | 20–25 °C |
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Points to Remember
Following are some important points:
- Hypobromous acid is weak as well as unstable acid.
- Hypobromous acid has a molecular weight of 96.911 g/mol.
- Hypobromous acid is also known as Bromanolor hydroxide bromine.
- Hypobromous acid is in +1 oxidation state.
- Hypobromous acid is used as disinfectants, Deodorants, Bleach, Oxidizing Agent, Germicidal agent in spas and hot tubs.
Sample Questions
Ques: Write the chemical formula of Hypobromous acid? (2 Marks)
Ans: HOBr is the chemical formula for Hypobromous Acid because hydrogen has one electron; Oxygen has six electrons and Bromine has seven electrons. One electron of hydrogen forms a pair with one electron of Oxygen and other one electron of Oxygen forms a pair with one of the electrons of bromide. After the pairing oxygen has four electrons unpaired and bromine has six electrons unpaired.
Ques: What is the acid strength of an acid and what is the value of strength of Hypobromous acid? (2 Marks)
Ans: The acid strength of an acid is defined as the ability of an acid to lose the H+ ions and an anion and is given by HA. Where H denotes the H+ ion and A denotes the Anions. The acid strength of Hypobromous acid is 8.65.
Ques: What is the chemical reaction of formation of Hypobromous Acid? (2 Marks)
Ans: Hypobromous acid is formed when Bromine reacts with water and the reaction of the same is as following:
Br2 + H2O ⇔ HOBr + HBr
Ques: Why does Hypobromous acid have +1 Oxidation State? (2 Marks)
Ans: At 20 °C, bromine gas reacts quickly with an aqueous hydroxide (such as sodium or potassium hydroxide) by the following reaction:
Br2(aq) + 2OH−(aq) ⇒ Br− (aq) + BrO−(aq) + H2O(l)
Bromine disproportionates (goes through both reduction and oxidation) from oxidation state 0 (Br2) to oxidation states –1 (Br) and +1 (BrO) in this reaction.
Ques: What are the chemical properties of Hypobromous Acid? (2 Marks)
Ans: The chemical properties of Hypobromous Acid is:
Hypobromous acid is a chemical substance with a molecular weight of 96.911 g/mol. Furthermore, the density of Hypobromous acid (HBrO), a chemical substance, is 2.470 g/cm. It has a pKa of 8.65, which indicates how acidic it is. Its boiling point is between 20 and 25 degrees Celsius.
Ques. What are the uses of Hypobromous Acid? (1 Mark)
Ans: Hypobromous acid is used as disinfectants, Deodorants, Bleach, Oxidizing agent, Germicidal agent in spas and hot tubs. Hypobromous Acid has the ability to kill pathogens and is hence used in Deodorants, as a Bleach, as an Oxidizer, and as a Disinfectant. It is also used as a germicidal agent in hot tubs and Spas
Ques: Why is Hypobromous Acid weak? (2 Marks)
Ans: Hypobromous acid is weak because the bromine molecule is loosely attached, Hypobromous acid is unstable and reacts quickly. Hypobromous acid, with the chemical formula HOBr and the bromine atom in the +1 oxidation state, is a weak, unstable acid. "Bromanol" or "hydroxide bromine" are other names for it.
Ques: Why is it called Hypobromite? (2 Marks)
Ans: BrO is the hypobromite ion, often known as alkaline bromine water. Bromine has an oxidation state of +1. Hypobromite is a bromine chemical similar to hypochlorites, which can be found in household bleaches and immunological cells. In many aspects, hypobromite is similar to hypochlorite, and it's likewise employed as a germicide and antiparasitic in both industrial and immune system applications.
Ques: What can be the colour of Hypobromous Acid? (1 Mark)
Ans. If a tank filled with 3,500 to 4,000 ppm of Hypobromous acid is left unattended for 3 days, Hypobromous acid will show orange colour.
Ques: Is HOBr soluble? (1 Mark)
Ans: Hypobromite is soluble in water and with a temperature range of 201K to 252K, Hypobromous acid is soluble in Sulfuric Acid. When Water is mixed with bromine, Hypobromous acid is obtained by the following reaction.
Br2 + H2O ⇔ HOBr + HBr
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