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Lithium Iodide is an inorganic compound consisting of a bond of lithium and iodine. The chemical formula of the compound is LiI. Lithium iodide is a white crystalline powder that changes colour to yellow when it comes in contact with air.
- The process of oxidation is responsible for converting the compound from iodide into iodine.
- Apart from this, lithium iodide can contribute to the formation of different hydrates.
- LiI crystallizes in the form of a NaCl motif (Sodium chloride motif).
- Mono-, de-, and tri-hydrate are some of the examples of lithium iodide hydrates.
- You can use it as a heat-transfer medium in molten salt reactors.
Key Terms: Lithium Iodide Formula, Lithium Iodine, Lithium Iodide, Lithium Iodide Structure, Preparation of Lithium Iodide, Lithium, Iodine, Lithium Sulfide, Properties of Lithium Iodide
Lithium Iodide Formula and Structure
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Lithium iodide is a chemical compound whose formula and structure is as follows:
Lithium Iodide Formula
Lithium iodide formula is LiI. The molecular weight of compound is 133.85 g/mol, whereas its density is 4.08 g/cm3. During the formation process of lithium iodide, Li+ (cat ion of lithium) reacts with I- (anion of iodine).
Lithium Iodide Structure
Lithium iodide forms a crystal lattice structure with a face-centred cubic arrangement. In the structure, each lithium-ion is surrounded by iodide ions. The lattice formed in the structure is repeated periodically in all three dimensions.
- Lithium iodide lattice structure consists of a high degree of ionic bonding.
- Due to its small size, lithium ions have high charge density, which results in the formation of strong bonds with larger iodide ions.
- A fraction of an atom is present at every corner of the cube.
- There are six other full atoms located at the centre of every face of the cube.
Structure of Lithium Iodide
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|---|---|---|
| Balance Chemical Equations | Sandmeyer Reaction | Enantiomers |
| Oxidizing Agent | Alliphatic Hydrocarbons | Mitsunobu Reaction |
Properties of Lithium Iodide
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The properties of lithium iodide are divided into physical and chemical properties, which are as follows:
Physical Properties of Lithium Iodide
The physical properties of lithium iodide are as follows:
- The crystalline solid powder has a melting point of 469°C.
- Lithium iodide is highly soluble in water.
- The boiling point of the substance is 1171°C.
- The chemical compound is also soluble in acetone, methanol, alcohol, and ammonia solution.
- It has a refractive index of 1.955.
The physical properties of lithium iodide are tabulated below:
| Category | Compound |
|---|---|
| Chemical Formula | LiI |
| Boiling Point | 2138-2174 °F, 1170-1190 °C, |
| Color | White |
| Appearance | Powder/Crystalline solid |
| State | Solid (at room temperature) |
| Refractive Index | 1.955 |
| Heat Capacity (C) | 0.381 J/g K or 54.4 J/mol K |
| Solubility | Soluble in acetone, methanol, alcohol, and water. |
| Water Solubility | 1510 g/L (at 0 °C), 1670 g/L (at 25 °C), 4330 g/L (at 100 °C) |
| Magnetic Susceptibility | -50 X 10-6 cm3/mol |
| Crystal Structure | Face-centered cubic (FCC) lattice structure |
Chemical Properties of Lithium Iodide
The chemical properties of lithium iodide are as follows:
Hygroscopicity
Lithium iodide is hygroscopic, so it easily absorbs moisture from the air. This results in the formation of a compound with water that is less crystalline in nature.
Reaction with Acids
LiI reacts with acids to produce lithium salts of that compound. When it reacts with sulphuric acid, it will produce lithium sulphate.
LiI+H2SO4→Li2SO4+2HI
Reaction with Oxidising Agents
Lithium iodide can be oxidised by reaction with oxidising agents such as chlorine Cl2 or bromine Br2. This results in the formation of lithium halides like lithium bromide or lithium chloride.
2LiI+Cl2→2LiCl+I2
2LiI+Br2→2LiBr+I2
Reaction with Alkali Metals
LiI react with alkali metals like potassium or sodium to form mixed halides. When lithium iodide reacts with sodium, then it will form sodium iodide.
Reaction with Organic Compound
The chemical compound is combined with an organic compound to form CO bonds. This results in the conversion of methyl esters into carboxylic acids.
RCO2CH3 + LiI → RCO2Li + CH3I
Preparation of Lithium Iodide
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There are two methods to prepare lithium iodide which are as follows:
Decomposition Reaction
We can get LiI by compounding lithium sulfide with strontium iodide. It is a double reaction. The decomposition reaction for the formation of LiI is:
Li2S + SrI2 → SrS + 2LiI
Reaction with Lithium Aluminium Hydride
Another method to prepare anhydrous or moisture-less LiI includes the reaction of iodine with lithium aluminum hydride in a diethyl-ether (a colorless transparent liquid) medium. The chemical reaction for this process is:
LiAlH4 + 2I2 → 2H2 + AlI3 + LiI
Reaction with Hydroiodic Acid
In this chemical reaction, lithium hydroxide react with yhdroiodic acid to produce lithium iodide and water. The reaction is as follows:
LiOH+HI→LiI+H2O
Reaction with Methyl Esters
When LiI is used in converting methyl esters to obtain carboxylic acid the following reaction takes place:
RCO2CH3 + LiI → RCO2Li + CH3I
Lithium Iodide Uses
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The various uses of lithium iodide are as follows:
- Lithium Iodide is a chemical used at the industrial level.
- It works as a solid-state electrolyte for batteries with high temperatures.
- As a standard electrolyte, LiI is used in batteries of machines like artificial pacemakers to make them long-lasting.
- It works as a separator for the bonds of carbon-oxygen in organic synthesis,
- For example, LiI can transform methyl esters into carboxylic acid.
- Apart from this, Lithium Iodide was previously used for CT scans as a radiocontrast element.
- Nowadays, they do not use the chemical because of renal toxicity.
- The chemical can also be used in combination with iodine in the electrolyte of dye-synthesized solar cells.
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|---|---|---|
| Cannizzaro Reaction Mechanism | Elimination Reaction | Nucleophilic |
| Stereochemistry | Optical Isomerism | Wurtz Reaction |
Things to Remember
- Lithium iodide is a non-combustible compound that is more electronegative in nature.
- The solubility of LiI at 0 °C is 1510 g/L, whereas at 100 °C is 4330 g/L.
- It can decompose after heating, which may induce corrosive gasses.
- When LiI is mixed with water or liquified, the water molecules stabilize the ions.
- The energy released is higher than Lithium Iodide’s lattice energy.
- Thus, the solution of LiI is exothermic in nature.
- It is used as a phosphor in neuron detection.
- Lithium iodide can also be used as a separator to cleave C-O bonds.
Sample Questions
Ques. LiI is highly soluble in ethanol than KI. Justify? (3 marks)
Ans. LiI is highly soluble in ethanol because of its small structure. Polarizing power of the lithium ion is higher than that of the potassium ion. Also, the iodide ion electron cloud can be polarized at a higher extent compared to the potassium ion. As a result, LiI has a higher covalent character than KI. Thus, it is highly soluble in ethanol.
Ques. Why LiI is more covalent as compared to lithium fluoride? (2 marks)
Ans. Lithium fluoride is also an inorganic compound like lithium iodide. It is in the form of colorless solid which changes to white color with reducing crystal size. Fazan’s rule states that, the ion of lithium can polarize I- ion with a greater capacity than that of F- ion. The large size of the anion makes LiI more covalent than lithium fluoride.
Ques. Which gases are released on the burning of lithium and why? (2 marks)
Ans. Lithium, when heated in air, gives out monoxide. It is because of the smaller size of Li+. A powerful positive field pulls the negative charge in such a way that it does not allow the oxygen ion to group up with other oxygen ion. Thus monoxide is released when lithium is burnt in air.
Ques. The name LiI is used for which chemical? (4 marks)
Ans. The name of a compound relies on the element which together forms that compound. The compounds which form because of the transfer of electrons are known as ionic compounds.
- The formation of such compounds occurs between a not-metal and a metal.
- While naming an ionic compound, the anion is named after the name of anion, where, anion is a positive charge and cation is a negative one.
- The name given in the question in LiI, which is a formula for lithium and iodine.
- Apart from this, lithium is a metal that transforms into a cation.
- Iodine is a not-metal halogen, it carries one electron in order to form iodide anion.
- Thus, the name will have lithium first followed by iodine as iodide, together forming lithium iodide.
Ques. LiI comes in more covalent nature than lithium chloride. Why? (2 marks)
Ans. The use of electronegativity in halogens makes LiI more covalent in nature than that of lithium chloride. The sequence of electronegativity is F>Cl>Br>I. In halogens, fluorine is highly electronegative while iodine is the lowest. The covalent character of bond elevates the group so it is F. As a result, iodide is more covalent in nature than lithium chloride.
Ques. Lithium iodide is which type of compound? Justify your answer by means or ionic or covalent. (4 marks)
Ans. Structure of a compound defines whether it is ionic or covalent in character. If the compound has a minimum of one ionic bond, it is known as an ionic compound. Whereas, all bonds are covalent in a covalent compound.
- Also, the bond can be called covalent if the electronegativity difference among two atoms is lower than 1.8.
- In LiI, the chemical bond is between lithium and iodine.
- The electronegative of Li is 2.1, and for I it is 2.5.
- Thus, the electronegativity difference amid lithium and iodine is 0.4, and the chemical bond is covalent.
- This makes LiI a covalent compound.
Ques. Water solubility of LiI is higher than LiF. Why? (5 marks)
Ans. Lithium comes at third place in the periodic table and holds small atomic radii. Solubility of the compounds relies on the lattice enthalpy. The cat ion is same for both the given elements.
- Even more, the anion nature makes a difference in the property of both the elements.
- When it comes to solubility, it focuses on mainly two conditions, lattice enthalpy and hydration enthalpy.
- In the case of lithium fluoride, lithium and fluorine both have the same atomic radii.
- But they are as small in size as that of I in the LiI.
- Due to its the small size, there is higher lattice energy.
- Even more, the close arrangement of ions increases the electrostatic attraction.
- Whereas in LiI, the lithium and iodine atoms have a big difference in the size of atoms.
- The atom of iodine is larger than fluorine, and LiI has lower lattice enthalpy.
- LiF will have less hydration energy which makes it less or insoluble in water. I
- n LiI, the lattice energy is low and hydration enthalpy is very high which makes it soluble in water.
Ques. Lithium matches with some properties of magnesium. Mention any two similar properties? (2 marks)
Ans. Both lithium and magnesium are light and hard in nature than other elements of their group. Secondly, both elements form ionic nitrides when burned in the nitrogen atmosphere. Lithium has similar properties like magnesium because of its ionic and atomic radii.
Ques. How is Li stored? Why is kerosene not used to store it? (1 mark)
Ans. While storing lithium, it is wrapped in paraffin wax. Kerosene cannot be stored using kerosene because it has low density, and can float on kerosene’s surface.
Ques. Where can lithium iodine batteries be used? (2 marks)
Ans. Li-ion or lithium ion batteries can be used in various products like toys, wireless earphones, electronic devices, small as well as large appliances. These batteries can also be used in electrical energy storage systems and electric vehicles.
Ques. What are the safety measures an individual must take while using lithium iodide? (3 marks)
Ans. In case LiI comes in direct contact of eyes, it is recommended to splash eyes with fresh water. The person should visit an eye care clinic, as early as possible, to avoid further damages. In the case of inhalation of Lithium Iodide, take the person to a ventilated place or fresh air place. Sometimes, the person may face breathlessness. In such situations artificial respiration can be a lifesaver. But use of mouth-to-mouth artificial respiration technique can be risky. One can use CPR masks or other medical devices for respiration.
Ques. What are the health hazards of lithium iodide? (2 marks)
Ans. Repeated or extensive exposure to LiI can lead to skin problems, including irritation. In case of contact with the eyes, the chemical could result in severe eye damage. Apart from this, ingestion or inhalation of LiI can badly affect health and cause serious injuries. Lithium hydroxide's fumes can lead to corrosion or irritation if burned. Being a highly reactive chemical, the containers of LiI can explode when heated.
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