Lead Iodide Formula: Definition, Preparation, Properties, Uses

You have landed on the right page to learn about Lead Iodide Formula. Lead iodide is an inorganic salt with the chemical formula \({\text{Pb}}{{\text{l}}_2}.\) Lead iodide is also written as lead \(\left({{\text{II}}} \right)\) iodide. It appears as a bright yellow powder at room temperature, which becomes yellow when heated.

Formerly, lead iodide was called plumbous iodide. It is an ionic compound. When heated, the colour turns to orange and then to red. It’s odourless and denser than water. It isn’t soluble in water. It is frequently used in photography, printing, and the production of solar cells, among other things. A reaction known as a twofold displacement reaction can be used to make it. In this article, let’s discuss everything about lead iodide in detail.

Lead Iodide Chemical Formula

The chemical formula of lead iodide is \({\text{Pb}}{{\text{l}}_2}.\) It contains lead and iodine atoms. An ionic bond between the lead and iodine atoms. That is, during the formation of lead iodide, the transfer of electrons between lead and iodine atoms takes place. Therefore, it is considered an ionic compound.

Lead iodide can be represented as,

or

The molar mass of lead iodide is \(461.01{\mkern 1mu} \,{\rm{g}}/{\rm{mol}}.\)

Lead Iodide Chemical Formula Derivation

The chemical formula of lead iodide can be derived using the criss-cross method.

In criss-cross methods, by knowing the valencies of the individual components, we can write its chemical formula. The symbol of the positive part is written on the left, and that of the negative part is written on the right side. The valencies of the individual components are interchanged and written as subscripts. Generally, subscript one is not written and signs of the charges are neglected.

With the help of the above section, the chemical formula of lead iodide can be written as,

Explanation: Lead iodide contains lead \(\left({{\text{P}}{{\text{b}}^{2 + }}} \right)\) and iodide \(\left({{{\text{I}}^ – }} \right)\) radicals. The valency of lead radical is two, and that of iodide radical is one. By criss-crossing these valency numbers, we can write the chemical formula of lead iodide as \({\text{Pb}}{{\text{l}}_2}.\)

Preparation of Lead Iodide

Lead iodide can be prepared using the following methods:

1. By the Reaction between Potassium Iodide and Lead Nitrate

Lead iodide is produced by the reaction of potassium iodide and lead nitrate in a water solution. The chemical equation for the reaction can be written as:

\({\text{Pb}}{\left({{\text{N}}{{\text{O}}_3}} \right)_2} + 2{\text{KI}} \to {\text{Pb}}{{\text{l}}_2} + 2{\text{KN}}{{\text{O}}_3}\)

The above reaction is a precipitation reaction. The potassium nitrate formed is soluble, and potassium iodide is insoluble at room temperature. As a result, it precipitates out. The above reaction can be employed using other salts containing lead \(\left({{\text{II}}} \right)\) and iodides such as sodium iodide or lead \(\left({{\text{II}}} \right)\) acetate.

For example, lead acetate reacts with potassium iodide to form lead iodide as,

\({\rm{Pb}}{\left( {{\rm{C}}{{\rm{H}}_3}{\rm{COO}}} \right)_2} + 2{\rm{KI}}\, \to \,{\rm{Pb}}{{\rm{l}}_2} + 2{\rm{C}}{{\rm{H}}_3}{\rm{COOK}}\)

2. By the Reaction between Lead Sulphide and Iodine

By the reaction of lead sulphide with iodine vapours, we can produce lead iodide. The chemical equation for the reaction can be written as:

\({\rm{PbS}} + {{\rm{I}}_2} \to {\rm{Pb}}{{\rm{l}}_2} + {\rm{S}}.\)

Properties of Lead Iodide

Let us discuss the physical and chemical properties of lead iodide:

Physical Properties of Lead Iodide

1. Lead iodide appears as a bright yellow powder. It is odourless too.
2. Lead iodide is almost insoluble in water, ethanol and cold hydrochloric acid.
3. It is denser than water.
4. It is soluble in alkalis, potassium iodide solution and in methyl isopropyl ketone.
5. The melting point of lead iodide is approximately equal to \(675\,{\text{K}},\) and its boiling point is approximately equal to \(1227\,{\text{K}}{\text{.}}\)
6. The density of lead iodide is \(6.16{\mkern 1mu} \,{\rm{g}}/{\rm{c}}{{\rm{m}}^3}.\)

Study System of Classification

Chemical Properties of Lead Iodide

The different chemical properties of lead iodide can be given as:

1. The action of Air

1. Lead iodide will get oxidized into elemental iodine in the presence of air. The chemical equation for such oxidation reaction can be given as,

\(2{\text{Pb}}{{\text{l}}_2} +{{\text{O}}_2} \to 2{\text{PbO}} + 2{{\text{I}}_2} \uparrow \)

2. At moderately high temperatures, lead iodide is decomposed by light. The decomposition products are metallic lead and iodine gas. This effect is used in patented photographic processes.
3. When bright yellow lead iodide is heated, it becomes orange or red.
4. The reaction of Lead Iodide with Sodium Hydroxide

Sodium trihydroxoplumbate \(\left({{\text{II}}} \right)\) and sodium iodide are produced when lead iodide reacts with sodium hydroxide. The chemical equation for the reaction can be given as,

\({\text{Pb}}{{\text{l}}_2} + 3{\text{NaOH}} \to {\text{Na}}\left[{{\text{Pb}}{{\left({{\text{OH}}} \right)}_3}}\right] + 2{\text{Nal}}\)

5. The reaction of Lead Iodide with Sulphuric Acid

Lead iodide reacts with sulphuric acid to form lead sulphate, iodine, water and hydrogen sulphide. The chemical equation for the reaction can be given as,

\(4{\text{Pb}}{{\text{l}}_2} + 5{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to 4{\text{PbS}}{{\text{O}}_4} + 4{{\text{I}}_2} + {{\text{H}}_2}{\text{S}} + 4{{\text{H}}_2}{\text{O}}\)

Uses of Lead Iodide

Lead iodide has got several uses, and they are:

1. Lead iodide is used as a precursor material in the manufacture of solar cells.
2. It is also used as a photon detector in \({\text{X}}\)-rays and gamma rays.
3. The photolytic decomposition of lead iodide is used in photographic processes.
4. As a yellow pigment, lead iodide was used in paints. However, due to its high toxicity and poor stability, its use as a pigment is banned.
5. In art, it is used for bronzing.
6. In aerosols, it is used for cloud seeding.
7. For far-infrared astronomy, it is used as a filter.
8. It is also used in electrosensitive recording papers, lubricating greases, etc.
9. Along with thiols, it is used in photographic emulsions.
10. Lead iodide is also used in thermoelectric applications.

FAQs

Q.1. What is the chemical formula of lead iodide?
Ans: The chemical formula of lead iodide is \({\text{Pb}}{{\text{l}}_2}.\) It is an ionic compound.

Q.2. How can we write the formula of lead iodide?
Ans: The chemical formula of lead iodide can be written using the criss-cross method. Lead iodide contains lead \(\left({{\text{P}}{{\text{b}}^{2 + }}} \right)\) and iodide \(\left({{{\text{I}}^ – }} \right)\) radicals. The valency of lead radical is two, and that of iodide radical is one. By criss-crossing these valency numbers, we can write the chemical formula of lead iodide as \({\text{Pb}}{{\text{l}}_2}.\)

Q.3. What is \({\text{Pb}}{{\text{l}}_2}\) used for?
Ans: \({\text{Pb}}{{\text{l}}_2}\) is lead iodide. It has got several uses. It is used in the photographic processes, photon detectors, pigments, photographic emulsions, etc.

Q.4. Is lead iodide safe?
Ans: Lead iodide is a carcinogen and is toxic too. Therefore, it is not at all safe for humans.

Q.5. Does lead iodide dissolve in water?
Ans: Lead iodide is insoluble in water. Therefore, it will not dissolve in it. It dissolves in alkalis.

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