Key Properties and Applications of Hydrobromic Acid
Dissolving diatomic molecules, hydrogen bromide in water gives us hydrobromic acid. Its molecular name (chemical formula) is HBr. There is a simple, single covalent bond between Bromine and Hydrogen atoms. As Bromine has a high electronegativity, the bond gets ionized easily. It makes HBr a very strong acid. It readily fumes when exposed to moist air. It is generally transported in a liquified compressed gas form. The HBr acid is commercially available in diluted form (48% acid+ 62% solution).
Hydrobromic Acid (Hbr acid) is also known as Hydronium Bromide, Bromane.
Atomic Structure of HBr
The chemical formula for HBr acid is HBr or BrH.
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Production of HBr Acid
The hydrobromic acid can be produced in laboratories.
When bromine, sulfur dioxide, and water react, sulphuric acid and hydrobromide gas are produced.
\[Br_{2}\] + \[SO_{2}\] + 2 \[H_{2}\]O → \[H_{2}\] \[SO_{4}\] + 2 HBr
An alternative method for producing The HBr acid in the lab is to mix dilute sulphuric acid with potassium bromide. This method is widely used for industrial production. The chemical expression is as shown below,
\[H_{2}\]\[SO_{4}\] + KBr → \[KHSO_{4}\] + HBr
Physical Properties of HBr
Chemical Properties of HBr
1. It is highly corrosive to metals and fabrics.
2. When HBr reacts with sulphuric acid, Sulphur dioxide, bromine, and water forms. The chemical equation can be written as
2HBr + \[H_{2}\]\[SO_{4}\] → \[Br_{2}\]+ \[SO_{2}\]+ \[2H_{2}\]O
3. When HBr reacts with propene, the result is the formation of 2- Bromopropane. The chemical expression is written as,
HBr+ \[C_{3}\]\[H_{6}\] → \[C_{3}\]\[H_{7}\]Br
4. It decomposes when heated and produces toxic fumes.
5. It is denser than air.
6. Its pH value is less than 2.
7. Its pKa value is less than -2
8. The HBr acid is incompatible with ozone and fluorine.
9. The HBr acid is not combustible by itself.
10. If exposed to heat for a longer time it can lead to an explosion.
11. The fumes of hydrobromic acid are oxidizing and can cause corrosion of wood, paper, oil, clothes, and metals.
12. When the HBr acid reacts with alkenes violent polymerization occurs.
13. Dilution of HBr gas in water can cause the generation of Heat.
14. When it comes in contact with metals, it releases flammable hydrogen gas.
15. The HBr acid neutralizes amines and inorganic hydroxides, that form salts. As the process generates heat, it should be avoided to carry out in small spaces.
16. Reacting with aluminium and iron, it produces toxic gases.
17. Fumes of HBr form clouds in a humid atmosphere.
18. When it reacts with nitrites and sulfites, it releases carbon dioxide. Though it is not toxic, heat and splashing of reaction can be hazardous.
19. It is utilized in creating inorganic bromides such as those of sodium, calcium and zinc.
20. Most preparation in the lab is done with an anhydrous compound of HBr which gets dissolved in water.
Uses of HBr Acid
HBr acid is widely used
As a catalyst and reagent in many organic preparations.
In many industrial processes such as dehydration, isomerization, hydration, polymerization.
Bromine based fumigants are used in sanitation and for disinfection treatments.
Bromide salts are found in medications.
In the extraction of mercury from cinnabar ore.
As a key raw material in the production of photosensitive materials, dyes, inorganic pharmaceutical products.
In the production of Bromium compounds that are further used in dyes, insecticides, plastic castings.
Also used widely in modern manufacturing and in various components in combination with other substances. Used to make medicines to fuels, plastics, semiconductors.
Fun Facts
HBr is a gas, but when it is dissolved in water, it becomes liquid.
In the past, diluted bromides were widely used as anti-epileptic and sedatives medicines.
To increase the storage life of fruits and vegetables, Hydrobromic acid(diluted) is used in post-harvest treatments of horticulture.
In the US, traces of bromide were found in food. It was the main cause of higher bromide exposure.
Different kinds of HBr ionization research on ice surfaces help in finding out about ways of ozone depletion in the Arctic atmosphere. This is one of the important factors for considering atmospheric chemistry.
Did You Know
William W. Carlin discovered the HBr Acid. He patented the process of creation of the acid on July 28th, 1977.
FAQs on Hydrobromic Acid: Complete Chemistry Guide
1. What is hydrobromic acid, and how is it different from hydrogen bromide?
Hydrobromic acid is the aqueous solution of the gas hydrogen bromide (HBr). The key difference is the physical state and context: Hydrogen bromide (HBr) is a diatomic molecule in its gaseous form. When this gas is dissolved in water, it ionises completely to form hydrobromic acid (H₃O⁺ and Br⁻ ions), which is a strong mineral acid. So, HBr(g) is the pure compound, while HBr(aq) is the acid.
2. Why is hydrobromic acid considered a strong acid?
Hydrobromic acid is considered a strong acid because it completely dissociates or ionises in an aqueous solution. The covalent bond between hydrogen (H) and bromine (Br) is highly polar and relatively weak. When HBr dissolves in water, this bond breaks easily, releasing a proton (H⁺) which is donated to a water molecule. This high degree of ionisation to form hydronium ions (H₃O⁺) is the defining characteristic of a strong acid.
3. What are the key physical properties of hydrobromic acid?
The physical properties of hydrobromic acid depend on its concentration, but key characteristics include:
- Appearance: It is a colourless or faintly yellow corrosive liquid.
- Odour: It has a pungent, acrid smell.
- Boiling Point: The constant-boiling azeotropic mixture (about 47.6% HBr by mass) boils at approximately 124.3 °C.
- Molar Mass: The molar mass of the HBr molecule is approximately 80.91 g/mol.
- Density: The density of the aqueous solution is greater than water, typically around 1.49 g/cm³ for the 48% solution.
4. How does the acidic strength of hydrobromic acid compare to other hydrohalic acids like HCl and HI?
The acidic strength of hydrohalic acids increases down the group in the periodic table. Therefore, the order of strength is: HI > HBr > HCl > HF. This trend is determined by the bond dissociation enthalpy, not electronegativity. The H-I bond is the weakest and longest, making it the easiest to break and donate a proton. The H-Br bond is weaker than the H-Cl bond, making hydrobromic acid a stronger acid than hydrochloric acid but weaker than hydroiodic acid.
5. What is a common laboratory method for the preparation of hydrobromic acid?
A common laboratory method for preparing hydrobromic acid involves the reaction of an alkali metal bromide, such as sodium bromide (NaBr) or potassium bromide (KBr), with a non-oxidising strong acid like phosphoric acid (H₃PO₄). The mixture is heated to produce hydrogen bromide gas, which is then dissolved in water to form hydrobromic acid. The reaction is:
3NaBr + H₃PO₄ → 3HBr + Na₃PO₄.
6. Why can't hydrobromic acid be prepared by reacting sodium bromide (NaBr) with concentrated sulfuric acid (H₂SO₄)?
This is a classic conceptual trap. While the initial reaction does produce HBr, concentrated sulfuric acid (H₂SO₄) is a strong oxidising agent. It will oxidise the newly formed hydrogen bromide into bromine gas (Br₂), which is a reddish-brown vapour. The reaction is 2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O. Because of this unwanted side reaction, a non-oxidising acid like phosphoric acid is used instead for a pure yield of HBr.
7. What are the main industrial uses and chemical applications of hydrobromic acid?
Hydrobromic acid is a vital reagent in chemistry with several important applications, such as:
- Synthesis of Bromides: It is used to produce inorganic bromides (e.g., ZnBr₂, CaBr₂) and organic bromides (alkyl bromides).
- Catalyst: It acts as a catalyst in certain alkylation and oxidation reactions.
- Pharmaceuticals: It is used as a precursor in the synthesis of various pharmaceutical drugs.
- Organic Reactions: A key application is in the anti-Markovnikov addition of HBr to alkenes in the presence of peroxide to form primary alkyl halides.
8. What are the necessary safety precautions for handling hydrobromic acid in a laboratory?
Handling hydrobromic acid requires strict safety measures due to its corrosive nature. Key precautions include:
- Always work in a well-ventilated fume hood to avoid inhaling its toxic fumes.
- Wear appropriate Personal Protective Equipment (PPE), including chemical-resistant gloves, safety goggles or a face shield, and a lab coat.
- Keep it stored away from incompatible materials, especially strong bases and oxidising agents.
- Ensure an eyewash station and safety shower are readily accessible in case of accidental contact.
9. What are the potential health hazards of being exposed to hydrobromic acid?
Exposure to hydrobromic acid is extremely dangerous. It is highly corrosive and can cause severe health effects:
- Inhalation: Breathing in the fumes can cause severe irritation to the nose, throat, and respiratory system, potentially leading to pulmonary edema.
- Skin Contact: Direct contact causes severe skin irritation and chemical burns.
- Eye Contact: Splashes can cause serious eye damage, including permanent blindness.
- Ingestion: Swallowing the acid leads to severe burns in the mouth, throat, and stomach.
