[Chemistry Class Notes] on Lead Iodide Formula Pdf for Exam

The salt lead(II) iodide, sometimes known as lead iodide, has the formula PbI₂. It is a bright yellow odourless crystalline solid at ambient temperature that turns orange and red when heated. It was previously known as plumbous iodide. The other name of lead is plumbum. Therefore, lead iodide is also called plumbous iodide. The name plumbous represents the +2 oxidation state of lead. Plumbous formula can be represented as Pb⁺².

Why is PbI₂ Formula of Lead Iodide known and PbI₄ Not?

PbI₂ is a known formula of lead iodide Because iodine levels in PbI₄ lead to the reduction of Pb(IV) while oxidising itself from iodide to iodine. Therefore, PbI₄ does not exist. This instability of PbI₄ leads to the generation of PbI₂. This also proves that iodide ion is a strong reducing agent for reducing Pb(IV) to Pb (II).

Preparation of Lead Iodide

In a water solution, PbI₂ is usually produced by precipitating potassium iodide KI and lead(II) nitrate Pb(NO₃)₂:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

While potassium nitrate KNO₃ is soluble at normal temperature, lead iodide PbI₂ is almost insoluble and consequently precipitates.

Other soluble salts containing lead(II) and iodide, such as lead(II) acetate and sodium iodide, can be used instead.

The chemical can also be made by reacting iodine vapour with molten lead at temperatures between 500 and 700 degrees Celsius.

By depositing a thin film of lead sulphide PbS and subjecting it to iodine vapour, a thin film of PbI₂ can likewise be made.

PbS + I₂ → PbI₂ + S

Following that, the sulphur is rinsed using dimethyl sulfoxide.

Structure of Lead Iodide

Properties of Lead Iodide

• The molecular formula for Lead iodide is PbI₂.

• The molecular weight of PbI₂ is 461.01 g/mol.

• The Density (mass/volume) of Lead iodide is 6.16 g/dm³.

• The Melting point of Lead iodide is 402 °C.

• Boiling point of Lead iodide is 953 °C.

• The colour of lead iodide is yellow. This yellow colour of lead iodide can only be seen in the precipitated form, it disappears in the solution form.

Application of Lead Iodide

Solar cells and X-ray and gamma-ray detectors are among the few specialised applications for the chemical now available. Its preparation is a fun and popular chemical demonstration that may be used to teach subjects like precipitation reactions and stoichiometry.  At somewhat high temperatures, it is dissolved by light, and this effect has been employed in a proprietary photography process.

Lead iodide, often known as iodide yellow, was once used as a yellow pigment in some painters. However, due to its toxicity and lack of stability, it is no longer widely used.

Did You Know?

• Lead iodide isn’t used as a precursor in the production of high-efficiency solar cells.

• Spin coating is used to apply a PbI₂ solution in an organic solvent, such as dimethylformamide or dimethyl sulfoxide, over a titanium dioxide layer.

• The layer is then annealed after being treated with a methylammonium iodide CH₃NH₃I solution, resulting in the double salt methylammonium lead iodide CH₃NH₃PbI₃, which has a perovskite structure.

• Lead iodide was formerly called plumbous iodide.