Zinc Bromide Formula – Structure, Properties, Uses, Sample Questions

Zinc Bromide consists of the elements Zinc and Bromine. Zinc is silvery-greyish brittle metal present in group-12 of the periodic table. It is the first element in group-12. Its atomic number is 30 and is represented by the symbol Zn. Zinc is one of the widely used metals. Bromine is a volatile red-brown liquid at room temperature which evaporates readily to form a similarly colored vapour. It is present in group-17 of the periodic table. Bromine’s atomic number is 35 and is represented with the symbol Br.

What is Zinc Bromide?

Zinc Bromide is an inorganic, non-flammable compound which is used as Lewis acid in organic chemistry. Its chemical formula is ZnBr₂. Zinc Bromide is a hygroscopic compound that is easily soluble in water and forms dihydrate as ZnBr₂. 2H₂O. It is a colourless salt which is soluble in water to form acidic solutions. Zinc Bromide is also soluble in organic solvents. IUPAC name of ZnBr₂ is Zinc Bromide. The other names of Zinc Bromide are Zinc (II) Bromide, Zinc dibromide.

Preparation of Zinc Bromide

Zinc Bromide is prepared by treating Zinc Oxide (or) Zinc metal with hydrobromic acid.

ZnO + 2HBr + H₂O → ZnBr₂·2H₂O
Zn + 2HBr → ZnBr₂ + H₂

The reaction of Zinc Oxide with hydrobromic acid gives dihydrate ZnBr₂·2H₂O. This compound can be dehydrated with hot CO₂ to give anhydrous material.

Structure of Zinc Bromide

The structure of Zinc Bromide (ZnBr₂) resembles the structure of Zinc Iodide (ZnI₂). Here Zn has a +2 charge and each Bromine ion has a -1 charge.

Zinc Bromide Structure

Properties of Zinc Bromide

Chemical Formula	ZnBr2
Appearance	White crystalline powder
Molecular weight	225.188 g/mol
Melting Point	394 °C
Boiling point	697 °C
Solubility	Soluble in alcohol, ether, acetone, tetrahydrofuran
Density	4.20 g/cm3

Uses of Zinc Bromide

• Zinc Bromide is used as an electrolyte in zinc bromide batteries.
• In organic chemistry, Zinc Bromide is used as Lewis acid.
• In oil and natural gas wells, Solutions containing zinc bromide (ZnBr₂) are used to displace drilling mud when transitioning from the drilling phase to the completion phase.
• It is used as a transparent film shield against radiation.

Sample Questions

Question 1: What happens when Zinc Bromide is dissolved in water?

Answer:

Zinc Bromide is an acidic inorganic salt which is soluble in water. The solution after dissolving it in water contain moderate concentrations of hydrogen ions and have pH value less than 7. This solution is used to neutralize the bases.

Question 2: Zinc Bromide is health hazardous?

Answer:

Yes, Zinc Bromide is hazardous to health. On contact it irritates and burns the skin and eyes and on breathing it irritates the nose & throat and cause coughing.

Question 3: Find the molecular weight of Zinc Bromide?

Answer:

Zinc Bromide consists of one Zinc atom and two Bromine atoms.

Atomic weight of Zinc element=65.38

Atomic weight of each Bromine element=79.904

Molecular weight of ZnBr₂ = (1 × 65.38) + (2 × 79.904)

= 225.188

Question 4: Is Zinc Bromide ionic or covalent compound?

Answer:

Zinc Bromide is an ionic compound. Ionic compound is formed between oppositely electrostatic charges. Zinc is a metal with two positive ions i.e. Zn⁺² and Bromine is a non metal with a negative ion i.e. Br^–. So it is an ionic compound.

Question 5: Where ZnBr₂ is used?

Answer:

Zinc Bromide is used in oil industry to displace mud. It is also used in electrolysis, catalysis, electrical industry and metalworking companies.

Question 6: How Zinc Bromide is prepared?

Answer:

Zinc Bromide is simply prepared by treating Zinc metal with hydrobromic acid. It can also be prepared by treating Zinc oxide with hydrobromic acid to give dihydrate Zinc Bromide which is dehydrated with hot Carbon dioxide to produce the resultant Zinc Bromide.