15 Facts on HF + FeCl2: What, How To Balance & FAQs

The HF + FeCl2, a reaction occurs within a weak acid and a chloride compound. Let us have a brief discussion on HF + FeCl2 reaction below.

HF is the chemical formula of hydrofluoric acid and consists of 1 H and 1 F atoms. FeCl2 is the ferrous (II) chloride or iron (II) chloride and consists of 1 Fe and 2 Cl atoms. FeCl2 is a solid white greenish color crystalline compound. HF is a fuming gas or liquid with no color but a pungent odor.

Let us take a look at more facts about HF + FeCl2 reaction, like the product, type and other combination of reactions, intermolecular force, conjugate base, net ionic equation, and various more facts and FAQs on it.

What is the product of HF and FeCl2?

The product of the HF and FeCl2 reaction is iron (ii) fluoride or ferrous fluoride (FeF2) and hydrogen chloride (HCl).

2 HF + FeCl2   → 2 HCl + FeF2

What type of reaction is HF + FeCl2?

The HF + FeCl2 undergoes a double displacement reaction which is also known as a metathesis reaction.

How to balance HF + FeCl2?

The HF + FeCl2 reaction is balanced with the help of the following steps:

  • The HF + FeClunbalanced reaction is as follows
  • HF + FeCl2 = FeF2 + HCl
  • In the above equation, both LHS and RHS do not contain the same number of elements
  • First, multiply the HF by 2 on LHS we get
  • 2 HF + FeCl2 = FeF2 + HCl
  • Second, multiply the HCl by 2 on RHS we get
  • 2 HF + FeCl2 = FeF2 + 2 HCl
  • Now, the above equation contains an equal number of elements on the reactant LHS side and product RHS side of the reaction.

HF + FeCl2 titration

The HF + FeCl2 has the following titration procedure,

Apparatus and Chemicals:

  • 2 to 3 test tubes
  • Test tube stand
  • Test tube holder
  • Glass rod or stirrer
  • Measuring cylinder
  • Conical flasks
  • Hydrofluoric acid
  • Ferrous chloride solution


The reaction shows the exchange of ions in the solution is known as a Double displacement reaction. The reactants are ionic in nature and also water-soluble. The product formed in this reaction is a solid precipitate and a gaseous compound and the ions of reactants get exchanged with each other to form a new product.


  • Two test tubes get sterilized or washed with distilled water and later dried and label both test tubes as 1 and 2.
  • Add 5 ml of FeCl2 solution in test tube 1 and note the color.
  • Add 5 ml of HF acid in test tube 2 and note the color.
  • In a conical flask add both the FeCl2 and HF solutions from test tubes 1 and 2.
  • Stir the solution in a conical flask using a stirrer.
  • Left the solution for sometimes as it is, without disturbing it.
  • Note the color change of the solution in a conical flask.
  • The color change of the solution may be due to the exchange of ions between HF and FeCl2.
HF FeCl2
HF and FeCl2 reaction

HF + FeCl2 net ionic equation

The net ionic equation for HF + FeCl2 chemical reaction is

Fe2+(aq) + 2 Cl(aq) + 2 H+(aq) + 2F(aq) = Fe2+(aq) + 2 F(aq) + 2 H+(aq) + 2 Cl(aq).

  • 2 HF (aq) + FeCl2 (aq)  = FeF2 (aq) + 2 HCl (aq)
  • Fe2+(aq) + 2 Cl(aq) + 2 H+(aq) + 2 F(aq) = Fe2+(aq) + 2 F(aq) + 2 H+(aq) + 2 Cl(aq)
  • Here, all the ions are spectator ions in this reaction, so there is no further reaction occurs.

HF + FeCl2 conjugate pairs

HF + FeCl2 is not a conjugate pair.

  • HF is can act as conjugate acid and F- can act as a conjugate base.
  • FeCl2 is produced due to the neutralization reaction of an acid and base and it acts as a Lewis acid and cannot show any conjugate acid-base pair.

HF and FeCl2 intermolecular forces

 The intermolecular force between the HF + FeCl2 is discussed below:

  • HF acid consists of the hydrogen bond intermolecular force as it can donate its proton which is attached with Fby a hydrogen bond.
  • FeCl2 is an ionic moiety, so it has an ion-ion interaction between two oppositely charged ions.

HF + FeCl2 reaction enthalpy

The reaction enthalpy for HF + FeCl2 chemical reaction is 188.79 kJ/mol.

  • The enthalpy of formation for HF is -272.72 kJ/mol.
  • The enthalpy of formation for FeCl2 is -341.79 kJ/mol.
  • The enthalpy of formation for FeF2 is -711 kJ/mol.
  • The enthalpy of formation for HCl is -92.3 kJ/mol.
  • The Reaction enthalpy (∆H) of HF + FeCl2 = Enthalpy of product – enthalpy of reactant, we get,
  • (H) of HF + FeCl2 is = -614.51 kJ/mol – (-803.3) kJ/mol
  • (H) of HF + FeCl2 is = 188.79 kJ/mol.

Is HF + FeCl2 a buffer solution?

HF + FeCl2 is not a buffer solution because it is not a combination of weak acid and base. HF is a weak acid while FeCl2 is a Lewis acid, thus they both cannot form a buffer solution. Only the compounds that act as weak acids, weak bases, conjugate bases, and salt are able to form a buffer solution.

Is HF + FeCl2 a complete reaction?

The HF + FeCl2 cannot show a complete reaction because there is no formation of equilibrium. This reaction contains two reactants and two products, also it contains FeCl2 which is not able to mix completely. As equilibrium is not formed the HF + FeCl2 reaction is not complete.

Is HF + FeCl2 an exothermic or endothermic reaction?

The HF + FeCl2 is an endothermic reaction. There is no heat produced during the reaction as HF is a weak acid and FeCl2 is a salt that acts as Lewis acid. The enthalpy change value for HF + FeCl2 reaction is positive which confirms that it is an endothermic reaction.

Is HF + FeCl2 a redox reaction?

The HF + FeCl2 is not a redox reaction due to the following points.

  • The oxidation number of H and F in HF is +1 and -1.
  • The oxidation number of Fe and Cl in FeCl2 is +2 and -1.
  • The oxidation number of Fe and F in FeF2 is +2 and -1.
  • The oxidation number of H and Cl in HCl is +1 and -1.
  • From the above values of oxidation numbers of reactants and products of HF + FeCl2 reaction, it is clear that there is no change in oxidation number.
  • The oxidation number of the reactant and product is the same in HF + FeCl2 reaction, so it is not a redox reaction.

Is HF + FeCl2 a precipitation reaction?

The HF + FeCl2 is a precipitation reaction. In this reaction, when HF is reacted with FeCl2, there is a formation of precipitates of a white color crystalline solid compound known as FeF2. The FeF2 is an inorganic complex compound formed as a white precipitate in this reaction.

Is HF + FeCl2 reversible or irreversible reaction?

The HF + FeCl2 shows an irreversible reaction because in this reaction, the reactants HF and FeCl2 can form products FeF2 and HCl but these products are not able to form the same reactants as a product again when gets reacted with each other.

Is HF + FeCl2 displacement reaction?

The HF + FeCl2 is a displacement reaction, rather it is a double displacement reaction. The oppositely charged ions of HF + FeCl2 reactants get exchanged or displaced during the formation of the product, which confirms that it is a displacement reaction.


The HF + FeCl2 is a double displacement reaction and has the formation of products iron (ii) fluoride with hydrogen chloride. It is an endothermic reaction and a precipitation reaction. The reaction enthalpy for HF + FeCl2 reaction is 188.79 kJ/mol. It is not a redox reaction.