Iron Chloride(FeCl2) Properties(25 Facts You Should Know)

Iron chloride is an inorganic solid, also known as Ferrous chloride in chemistry. Let us explore the array of properties of Iron chloride.

Iron chloride is a stable halide of Iron; thermodynamically more stable than FeCl₃(Ferric chloride). Iron chloride absorbs moisture from the air (hygroscopic in nature) and form hydrates.

We will discuss here the melting point, boiling point, conductivity, and reactivity of Iron chloride with detailed explanations.

FeCl₂ IUPAC name

The IUPAC name (International Union of Pure and Applied Chemistry) of FeCl₂ is Iron (II) chloride.

FeCl₂ chemical formula

The chemical formula of Ferrous chloride is FeCl₂. In this formula, Iron is the central atom that is singly bonded with two chlorine atoms.

FeCl₂ CAS number

The CAS registry number (Chemical Abstracts Service) of FeCl₂ is 7758-94-3.

FeCl₂ ChemSpider ID

The ChemSpider ID (chemical structure database) of FeCl₂ is 22866.

FeCl₂ chemical classification

• FeCl₂ can be classified as an inorganic compound.
• FeCl₂ is a dihalide of iron that is generally off-white in appearance and also forms dihydrate and tetrahydrate.

FeCl₂ molar mass

The molar mass of Iron chloride in anhydrous form is 126.75 g/mol. The molar mass of tetrahydrate is 198.81 g/mol.

FeCl₂ color

Iron chloride is a white crystalline solid. It is generally white hexagonal crystals that sometimes appear green.

FeCl₂ molar density

The molar density of FeCl₂ is 0.025 mol/cm³ as its density is reported as 3.16 g/cm³.

Compound	Formula	Density
anhydrous	FeCl2	3.16 g/cm3
dihydrate	FeCl2.2H2O	2.93 g/cm3
tetrahydrate	FeCl2.4H2O	1.39 g/cm3

FeCl₂ melting point

The melting point of FeCl₂ is 674 °C or 950 K or 1251 °F.

FeCl₂ boiling point

The boiling point of FeCl₂ is 1023 °C or 1269 K or 1873 °F.

FeCl₂ state at room temperature

FeCl₂ exists as a solid at room temperature.

FeCl₂ ionic/covalent bond

Ferrous chloride is an ionic compound. The large electronegative difference between the cation and anion makes it an ionic halide of Iron. However, the compound has also shown some covalent character which can be explained as per Fajans^` rules.

FeCl₂ ionic radius

The ionic radius of Fe²⁺ is found to be 77 pm.

FeCl₂ electron configurations

The arrangement of electrons in atomic or molecular orbitals around the nucleus of an atom is called electronic configuration. Let us study the electronic configuration of FeCl₂.

• In FeCl₂, the iron is in +2 oxidation state and it will have six electrons in the d sub-shell. So, its valence electronic configuration will be [Ar]3d⁶.
• Furthermore, since Fe is coordinated with two chlorine atoms, the electronic configuration of the chloride ion must be [Ne]3s²3p⁶.

FeCl₂ oxidation state

• The oxidation state of the central atom, Iron in FeCl₂ is +2.
• Each of the two Chlorine atoms is in -1 oxidation state.

FeCl₂ acidity

The aqueous solution of FeCl₂ is acidic.  The solution of Iron chloride is slightly acidic in nature with a pKa of 1.8 x 10^-7. This gives a pH of 3.9 for a 0.1 molar solution of FeCl_2.

Is FeCl₂ odourless

FeCl₂ has no specific odour.

Is FeCl₂ paramagnetic

The substances that are weakly attracted to the externally applied magnetic field are found to show paramagnetic behavior. Let us see if iron chloride is paramagnetic or not.

FeCl₂ is paramagnetic in nature. The central atom, Fe has four unpaired electrons in d-orbitals, making this compound paramagnetic.

FeCl₂ hydrates

FeCl₂ forms dihydrates (FeCl₂.2H₂O)and tetrahydrates (FeCl₂.4H₂O) that are pale green and green in color, respectively.

FeCl₂ crystal structure

FeCl₂ possesses hexagonal crystal lattice and the tetrahydrate of FeCl₂ has monoclinic crystal structure.

• The hexagonal crystal structure of FeCl₂ has the dimensions, a=b=3.51 Å, c=6.18 Å and γ= 120^°.
• The monoclinic crystal structure of tetrahydrate (FeCl₂.4H₂O) has the dimensions, a = 5.91 Å, b = 7.71 Å, c = 8.84 Å and β = 112°.

FeCl₂ polarity and conductivity

FeCl₂ is ionic in nature and produces ions in solution.

• FeCl₂ is polar in nature. Due to the high charge difference between iron and chlorine, it shows polarity.

• FeCl2 gets fully ionized in water producing Fe²⁺ and Cl^– ions. If electricity is passed through this solution, it conducts electricity. FeCl₂ behaves as a strong electrolyte in solution.

FeCl₂ reaction with acid

• FeCl₂ does not react with acid because FeCl₂ is stable in acids.

FeCl₂ reaction with base

FeCl₂ solution reacts with the base to form ferrous hydroxide and salt. It reacts with potassium hydroxide to give Ferrous hydroxide and potassium chloride.

  FeCl₂(aq)+ 2KOH(aq)   →     Fe(OH)₂(s)+ 2KCl(aq)

  FeCl₂(aq) + 2NaOH(aq) →   Fe(OH)₂(s) + 2NaCl(aq)

FeCl₂ reaction with oxide

• FeCl₂ reacts with oxygen to give FeCl₃ (Ferric chloride). On reaction with oxide above 250°C (523K), FeCl₂ undergoes oxidation to give FeOCl (Iron oxychloride) and FeCl₃ gas. The reaction is as follows,

2FeCl₂(s) + 1/2O₂(g) → FeOCl(s) + FeCl₃(g)

• FeOCl further reacts with oxygen to give Fe₂O₃ and chlorine gas;

       2FeOCl(s) + 1/2O₂(g) → Fe₂O₃(s) + Cl₂(g)

• Also, the gaseous FeCl₃ formed in the first step will also react with oxygen to form Fe₂O₃ and chlorine gas above 370°C (643K);

       2FeCl₃(g) + 3/2 O₂(g) → Fe₂O₃(s) + 3Cl₂(g)

FeCl₂ reaction with metal

On reaction with highly reactive metals like sodium, FeCl₂ undergoes displacement reaction.

  2Na(s) + FeCl₂(aq) → 2NaCl(aq) + Fe(s)

Conclusion

FeCl₂ is a hygroscopic white crystalline ionic compound that is highly soluble in water and has a very high melting point and good conductivity. Iron chloride is widely used in sewage water treatment. It also has applications in medicinal chemistry, textile industry and is often used as a precursor in organic synthesis.