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Ammonium Bromide is the ammonium salt of Hydrobromic acid (HBr). Its chemical formula is NH2Br. It is a white, odourless salt, usually prepared by a direct reaction between ammonia (NH3) and hydrogen bromide. In the presence of water and moisture, the isometric crystals of ammonium bromide change their colour into yellow. Ammonium bromide is highly soluble in water and it splits into NH4+ and Br- ions in an aqueous solution. It is mildly toxic upon direct inhalation although it leaves only a temporary uneasiness after exposure. In normal storage conditions, its formula is stable. Ammonium Bromide has multiple applications some of which are in pharmaceuticals, photography film preparation, fireproofing of wooden objects, lithography and biocides.
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Key Takeaways: ammonium Bromide, formula of ammonium bromide, preparation of ammonium bromide, hydrogen bromide.
Ammonium Bromide
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Ammonium Bromide is the ammonium salt of Hydrobromic acid. It is a white, odourless salt. The chemical crystallizes into colourless prisms with a salty taste. It is highly soluble in water and sublimes when heated. When it is exposed to air, it is observed to slowly assume a yellow colour as the oxidation of bromide ( BR-) to bromine (Br2). So, in other words. Ammonium bromide is a white salt that changes its colour to yellow upon exposure to air and water. The formula of Ammonium Bromide stays stable under advised storage conditions.
Ammonium Bromide
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Structural Formula of Ammonium Bromide
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Ammonium Bromide is an ammonium salt that is formed when an ammonium ion reacts with a bromide ion in a ratio of 1:1.
NH3 + HBr → NH4Br
The chemical structure of Ammonium Bromide is as follows-
Chemical structure of Ammonium Bromide
The ball-and-stick model of an ammonium ion and bromine anion is as follows-
Ball and Stick Model
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Preparation of Ammonium Bromide
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Ammonium Bromide can be obtained by the direct reaction between Hydrogen Bromide and Ammonia.
NH3 + HBr → NH4Br
It can also be prepared by the reaction of ammonia with iron(II) bromide or Iron (III) bromide, which is usually obtained by passing an aqueous solution of bromine over iron.
2NH3 + FeBr2 + 2H2O → 2NH4Br + Fe(OH)2
Properties of Ammonium Bromide
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The physical and chemical properties of Ammonium Bromide is given below in a tabular form
| Chemical Formula | NH4Br or BrH4N |
| Molecular Weight | 97.943 g/mol |
| Density | 2.429 g/cc at 25°C |
| Crystal structure | Isometric |
| Chemical names | Ammonii Bromidium, ammonium bromatum, Ammonium bromide |
| Boiling point | 452°C |
| Melting Point | 235° C |
| Solubility | In water its solubility is 78.3g/100g water at 25°C, it is also soluble in acetone, ammonia, ether etc. however, it is practically insoluble in ethyl acetate |
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Applications of Ammonium Bromide
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There are multiple useful applications of Ammonium Bromide. Some of them are as follows-
- Ammonium Bromide is used in the preparation of photographic films and plates.
- It is used in fireproofing wooden objects.
- It is also used in lithography and the process of inscription.
- Ammonium Bromide is used in many pharmaceutical preparations along with corrosion inhibitors.
- Ammonium Bromide with another appropriate oxidizer as an efficient biocide in various water systems in the industrial sector and wastewater to control microorganisms like bacteria, fungi and algae.
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Things to Remember
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- Ammonium Bromide is a white odorless salt that becomes colourless upon crystallization.
- When it is exposed to air, it slowly assumes a yellow colour as the oxidation of bromide (BR-) to bromine (Br2) state takes place.
- It is easily soluble in water and also dissolves in acetone, ammonia and ether with different degrees of solubility.
- The chemical formula of Ammonium Bromide is NH4Br. It is also known by the names of Ammonia Bromidium, ammonium bromatum, Ammonium bromide.
- Ammonium Bromide has various applications including the preparation of photographic films and plates, lithography, pharmaceuticals and biocides.
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Sample Questions
Ques: What is Ammonium Bromide? (2 marks)
Ans: Ammonium Bromide is a white, odourless ammonium salt of Hydrobromic acid. The chemical formula of it is NH4Br.
Ques: State preparation reaction of ammonium bromide. (2 marks)
Ans: Ammonium Bromide can be prepared by the direct reaction between Hydrogen Bromide and Ammonia. The chemical reaction is as follows-
NH3 + HBr → NH4Br
It can also be prepared by the reaction of ammonia with iron(II) bromide or Iron(III) bromide, which is usually obtained by passing an aqueous solution of bromine over iron.
2NH3 + FeBr2 + 2H2O → 2NH4Br + Fe(OH)2
Ques: Write down some applications of ammonium bromide. (3 marks)
Ans: The applications of ammonium bromide are many-fold. Some of them are given below-
- Ammonium Bromide is used in the preparation of photographic films and plates.
- It is used in fireproofing wooden objects.
- It is also used in lithography.
- Ammonium Bromide is used in many pharmaceutical preparations along with corrosion inhibitors.
- Ammonium Bromide with other appropriate oxidizers as an efficient biocide in various water systems.
Ques: What is the chemical formula of ammonium bromide? (2 marks)
Ans: Ammonium Bromide is the ammonium salt of the hydrobromic acid having ammonium and bromide ions in a 1:1 ratio. The chemical formula of the chemical is NH4Br.
Ques: State the reaction of ammonium bromide with water. (2 marks)
Ans: Ammonium Bromide is a strong electrolyte when put in water. It splits into NH4+ and Br- ions.
NH4Br → NH4+ (aq.) + Br-(aq.)
However, at an elevated temperature, ammonia decomposes to ammonia and hydrogen bromide.
Ques: Comment on the solubility of Ammonium Bromide. (2 marks)
Ans: Ammonium bromide is easily soluble in water. In water, its solubility is 78.3g/100g water at 25°C. It is also soluble in chemicals like acetone, ammonia, ether etc. however, it is practically insoluble in ethyl acetate.
Ques: Is Ammonium Bromide acid or a base? (2 marks)
Ans: Ammonium bromide is a salt of ammonia and hydrogen bromide. It is acidic in nature formed from the neutralization of strong acid (HBr) and a weak base (NH4OH). Thus, the aqueous solution of ammonium bromide is slightly acidic having a pH value of less than 7.
Ques: What happens when ammonia is treated with bromine? (2 marks)
Ans: Bromine reacts with ammonia to produce hexaammonia bromide trinitride and ammonium bromide. The reaction takes place at a temperature closer to -75°C. The chemical reaction is as follows-
3Br2 + 10 NH3 → Br3N.6NH3 + 3NH4Br
Ammonium bromide is produced as a white solid smoke.
Ques: What are the therapeutic uses of ammonium bromide? (2 marks)
Ans: Ammonium Bromide has been in use since the beginning of the 19th century. The salts were used in neurological and mental diseases including epilepsy. It has been widely used as a sedative and anticonvulsant. However, the therapeutic effect is usually close to that of the toxic effects, thus it has been replaced with other agents.
Ques: Is ammonium bromide toxic? (2 marks)
Ans: Ammonium Bromide is considered to have mild toxicity and it has been found to give temporary discomfort if inhaled or it comes into close contact with eyes. Although it is harmful if ingested in a large amount. It can be a potent mutagen to animals and humans.
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