Lead II Chloride Formula

Lead Chloride

This article specifically deals with the lead chloride formula as structural and chemical representation.it is an inorganic compound that possesses lead as a central atom with two chlorine atoms attached to it. Lead (ll) chloride is a white solid compound under ambient condition but otherwise, it is a crystalline colourless and odourless compound and is also a most important lead-based reagent.  Lead chloride formula which is also known as lead (ll) chloride formula is expressed as PbCl2. Cotunnite is a natural mineral form of lead (ll) chloride and thus it is a naturally occurring inorganic compound found in the form of mineral ore. It is insoluble in water but is readily soluble in solutions that contain chloride ions. Lead chloride is more stable than lead tetrachloride as lead belongs to group 4 where all the elements belonging to group 4 show two oxidation states as +4 and +2. But as we go down the group the stability for the +4 oxidation state reduces and the +2 oxidation states increases. Thus unlike CCl4 or SiCl4, PbCl4 is much less stable in nature and readily decomposes at room temperature to form a much stable PbCl2


Structure

The chemical formula for lead chloride is PbCl2  which is commonly known as lead chloride but its IUPAC name is lead (ll) chloride. The chlorine atoms are connected to central atom lead through covalent bonding with a bond angle of 98o and the isotopic bond distance of each of the chlorine atoms with the central lead atom is 2.44 Å. Now to explain the nature of the bond the electronic configuration of the molecules and the atoms of it needs to be taken into consideration. Now the lead atom has an atomic number 82 which means its electronic configuration will be [Pb] 6s2 4f14 5d10 6p2. Thus lead has two electrons in its outer shell to donate or share. On the other hand, chlorine has an atomic number 17 which means it has an electronic configuration of 1s2 2s2 2p6 3s2 3p5 which means there is an unpaired electron in the 3p orbital that makes the shell unstable and it needs an electron to complete its octane. Thus the two chlorine atoms share each of the two pair electrons of lead present in the 6s shell to complete the octane and hence becomes a stable molecule. The molecule lead (ll) chloride forms a bent structure. Thus the structural formula of lead chloride molecules is illustrated as follows.


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In each of the molecules present in lead (ll) chloride, each of the lead atom is surrounded by nine chloride ions like a tricapped triangular prism molecular geometry where nine atoms or group of atoms or ligands are arranged around the central atom in such a way that a triangular prism formed with one atom attached on each of the three faces of the triangle. In solid lead chloride molecules, six chloride ions are present in the vertices of the triangular prism with lead as the central atom and three beyond the surfaces of each rectangular prism faces. Thus the chloride ions are not equidistant from the central lead atom. Seven out of nine chlorine atoms are at 280 -309 pm whereas the other two chlorine atoms are at 270 pm. Thus PbCl2 forms an orthorhombic needle structure which is also known as orthorhombic dipyramidal with the point group is 2m / 2m / 2m. Each lead atom has a coordination number of 9. Thus the structural formula of lead chloride in terms of its coordinate geometry is illustrated below.


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Synthesis

When an aqueous solution of chloride compounds such as HCl or NaCl or KCl when added to any lead (ll) compound, lead (ll) chloride is synthesized. This reaction is known as double displacement or metathesis reaction. Examples of such reactions are as follows.

1. With Soluble Lead Compound

  1. Lead (ll) Nitrate : Pb(NO3)2 + 2NaCl (aq) → PbCl2 (s) + NaNO3 (aq)

  2. Lead (ll) Acetate : Pb(CH3COO)2 (aq) + HCl (aq) →  PbCl2 (s) + 2CH3COOH

2. With Insoluble Lead Compound

  1. Lead (ll) Carbonate : PbCO3 + 2 HCl (aq) → PbCl2 (s) + CO2 (g) + H2O (aq)

  2. Lead (ll) Dioxide : PbO2 (s) + 4 HCl (aq) → PbCl2 (s) + Cl2 (g) + 2 H2O (aq) 

  3. Lead (ll) Oxide : PbO (s) + 2 HCl (aq) → PbCl2 (s) + H2O (aq) 

When copper (ll) chloride is reduced in presence of lead metal to get lead (ll) chloride is a direct reduction reaction. The reaction is as follows.

1. Pb (s) + CuCl2 → PbCl2 (s) + Cu (s)

Lead (ll) chloride is also formed by direct chlorination by the action of chlorine gas on lead metal. The reaction is as follows.

1. Pb (s) + Cl2 (g)  → PbCl2 (s) 

Few of the physicochemical properties of lead (ll) chloride which is PbCl2 chemical name is as follows:-


Properties of Lead Chloride


Property Name

Value

Molar mass

278.10 g / mol

Chemical formula of lead chloride

PbCl2

appearance

White odourless solid

hardness

1.5 - 2mohs scale

density

5.85 g /cm3

Boiling point

950 oC or 1740 oF or 1220 K

Melting point

501 oC or 934 oF or 774 K

Crystal structure

orthorhombic , oP12

Space group 

Pnma No. 62

Solubility in water

0.99 g in 1L of water at 20 oC

Solubility product (Ksp)

1.7 x 10-5 at 20 oC

solubility

Slightly soluble in HCl and ammonia, insoluble in alcohol, soluble in hot water as well as in presence of alkali hydroxide and also soluble in concentrated HCl (>6M)

Magnetic susceptibility

-73.8 x 10-6 cm3 / mol

Refractive index

2.199

Std. molar entropy

135.98 J K-1 mol-1

Std. enthalpy of formation

-359.4 KJ / mol


Reactions

When chloride ions are added to the suspension solution of lead chloride it gives rise to the lead chloride complex ion in the solution. It is because the addition of chlorine ions or any ligand breaks the chlorine bridges that have given a polymeric framework to the solid lead chloride.

 PbCl2 (s) + Cl → [ PbCl3 ]

 PbCl2 (s) + 2Cl → [ PbCl4 ]2ー

When molten NaNO2  reacts with PbCl2  it give rise to PbO

PbCl2 (s) + 3 NaNO2 (l) → PbO + 2 NO + NaNO3 + 2 NaCl

Lead (ll) chloride is also used for the synthesis of lead (lV) chloride. In this reaction, chlorine is bubbled through an aqueous solution of lead (ll) oxide that is present in the aqueous solution of ammonium chloride forming an intermediate [NH4]2[PbCl6] that is further reacted with cold concentrated sulfuric acid in order to synthesis lead (lV) chloride in form of oil. Lead (ll) chloride is also used for the synthesis of PbO2 when it is treated with sodium hypochlorite (NaHCl) where a reddish-brown precipitate of PbO2 is achieved.


Uses

  1. By cation replacement reaction of lead (ll) chloride in molten state, lead titanate and barium lead titanate are synthesized that are widely used in ceramic industries.

X PbCl2 + BaTiO3 (s) → Ba1-xPbxTiO3 + x BaCl2

  1. PbCl2 is also used by the expats in formation of transmission glasses and in the formation of an ornamental glass known as aurene glass. When this ornamental glass is sprayed with PbCl2 in controlled condition it results in formation of an iridescent surface.

  2. Even though PbCl2 is very less soluble in HCl still it is used in service with HCl as an addition of anatomy (Sb) increases the corrosion resistance power.

  3. Pattinson’s white lead with formula PbCl2 . Pb(OH)2 is a form of white lead that is used in car paints. But these days due to its high health hazard, white lead is banned in many countries. 

FAQs (Frequently Asked Questions)

1. What is White Lead Chloride?

Ans. White lead chloride is also known as Pattinson’s white lead with formula PbCl2 . Pb(OH)2 which was initially used as a car paint agent but due to its high health hazard it is now banned in many countries.

2. Can Lead Chloride Form a Precipitate?

Ans. lead (ll)chloride can form a precipitate which is white in colour when chlorine ions are added to a solution of lead (ll) nitrate. Thus sodium chloride solution or other similar chloride solutions are used to produce chloride ions.

3. Is Lead (ll) Chloride Cation?

Ans. lead (ll) chloride is not necessarily a cation but the lead atom in the molecule can lose its two electrons present in 6s shell to form a cation whereas each of the chlorine atoms with one deficit electron in its 3p shell can gain an electron to complete its octane and thus acts as a cation.