Lithium Bromide

What is Lithium Bromide?

Lithium bromide is an ionic compound of lithium and bromine. Lithium is an alkali metal which has 3 electrons. Electronic configuration of lithium is 2,1. Thus, it has 1 electron in its valence shell. On the other hand, bromine is a non – metal which has 35 electrons in its single atom. Its electronic configuration is 2,8,18,7. Thus, it has 7 electrons in its valence shell. Lithium can attain electronic configuration like nearest noble gas He by donating its one electron while bromine can attain electronic configuration like nearest noble gas Kr by accepting one electron. So, Li donates one electron to bromine and forms an ionic bond. Thus, both the elements get stability by attaining electronic configuration like nearest noble gas and form a new compound LiBr. 

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Lithium bromide is a hygroscopic chemical compound. Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. lithium bromide absorbs the moisture from the surrounding. That is why it is used as desiccant. 


Properties of lithium Bromide 

Physical and chemical properties of lithium bromide are listed below –

  • Its chemical formula is LiBr

  • Boiling point of lithium bromide is 1265 .

  • Melting point of lithium bromide is 552 .

  • It is a hygroscopic white solid. 

  • Its molar mass is 86.845 g/mol.

  • Its density is 3.464 g/cm3.

  • It is soluble in water. Its solubility in water increases, as the temperature increases. For example, its solubility in water is 143 g/100 ml at 0 and as the temperature reaches up to 20 , its solubility becomes 166.7 g/100ml. 

  • It is also soluble in methanol, ethanol, ether, acetone etc. It is slightly soluble in pyridine. 

  • It is not flammable. 

  • It can dissolve many polar organic compounds such as cellulose.

  • It is stable in nature and generally, does not react easily. 

  • Its anhydrous form forms cubic crystals like NaCl.

  • Reaction with chlorine – Lithium bromide reacts with the chlorine molecule and forms lithium chloride salt and bromine gas. Reaction is given below –

Cl2 + 2LiBr → Br2 + 2LiCl 

  • Reaction with silver nitrate – Lithium bromide reacts with silver nitrate and forms lithium nitrate and silver bromide. Reaction is given below –


Structure of Lithium Bromide 

In lithium bromide an ionic bond is formed by the transfer of an electron from lithium to bromine. As lithium donates an electron so it forms a cation or gets a positive charge Li+. While bromine accepts an electron, so it forms an anion or gets a negative charge Br-. Crystal structure of lithium bromide is cubic. 

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LiBr

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Crystal structure of anhydrous LiBr

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3D ionic structure of LiBr


Production of Lithium Bromide 

Lithium bromide can be prepared by many methods. Few of them are listed below –

  • By reaction of lithium carbonate and hydrobromic acid – Lithium bromide can be prepared by reaction of lithium carbonate with hydrobromic acid. Reaction is given below –

Li2CO3 + 2HBr 🡪 2LiBr + H2CO3

  • By reaction of lithium hydroxide and hydrobromic acid – Lithium bromide can also be prepared by reaction of lithium hydroxide with aqueous solution hydrogen bromide or hydrobromic acid. Reaction is given below –

LiOH + HBr 🡪 LiBr + H2O


Uses of lithium Bromide 

Lithium bromide is used in many fields. Few of its uses are listed below –

  • It is used in air – Conditioning machines as desiccants due to its hygroscopic nature. It is used with water in absorption chilling in air conditioners. 

  • It is used in synthesis of many organic compounds. 

  • It is used in pharmaceuticals in synthesis of many drugs.

  • It is used to produce many inorganic compounds as well such as lithium chloride etc. 

  • It was used as sedative in the early 1900s but due to some adverse effects on heart, doctors stopped using it as sedative. 

  • Lithium chloride and lithium bromide were used for the treatment of bipolar disorder. 

  • It is used in synthesis of olefins for catalytic dehydrohalogenation.

  • It is used in refrigerators as a non - CFC alternative as due to its hygroscopic nature it can easily absorb excess vapor. Thus, it makes the system environment friendly. 

  • It is used in emulsions as it is soluble in ether and other organic solvents. 


Health Hazards of Lithium Bromide 

As the studies have shown overuse of lithium bromide in drugs can cause heart attack and death. So, it must be used vigilantly and carefully. Generally, lithium salts are psychoactive and lithium bromide is also a lithium salt. 

It is corrosive in nature. It produces heat violently when dissolved into water as it has a negative enthalpy of dissolution. 


Lithium Bromide Summary in Tabular Form 

Lithium Bromide 

Chemical formula 

LiBr 

IUPAC Name 

Lithium bromide 

Molar mass 

86.845 g/mol

Appearance 

White solid 

Crystal Structure 

Cubic like NaCl 

State at STP

Solid 

Melting point 

552 ℃ 

Boiling point 

1265 ℃ 

Solubility in water 

Soluble (Solubility increases with temperature)

Solubility in organic solvents 

Soluble in acetone, ether, methanol and ethanol

Preparation 

By reaction of lithium carbonate and hydrobromic acid –

Li2CO3 + 2HBr 🡪 2LiBr + H2CO3

By reaction of lithium hydroxide and hydrobromic acid –

LiOH + HBr 🡪 LiBr + H2O

Main properties 

Hygroscopic 

Main use 

As desiccant 

Disadvantage 

Can be lethal, can cause bipolar disorder


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