15 Facts on HCl + Fe2S3: With Several Elements Reaction

Hydrochloric acid consists of two chlorine atoms joined by a polar covalent bond to form a diatomic compound. Let us examine the chemical reaction between HCl and Fe2S3.

Hydrogen chloride is dissolved in water and is a crucial chemical molecule for laboratories and a crucial acid for numerous reactions. Chemically, iron(III) sulphide has the formula Fe2S3. Iron(III) sulphide is a moderate water and acid-soluble iron source that can be used with sulphates.

In this article, we will examine the reaction of HCl + Fe2S3 as well as enthalpy, conjugate pairs, and titration.

What is the product of HCl and Fe2S3?

Iron(II) chloride(FeCl2), sulfur(S), and hydrogen sulphide(H2S) are the three primary byproducts formed when hydrochloric acid(HCl) and iron(III) sulphide(Fe2S3) combine.

HCl + Fe2S3 → FeCl2 + H2S + S

What type of reaction is HCl + Fe2S3?

HCl + Fe2S3 is a redox reaction in which the reactant undergoes both oxidation and reduction simultaneously. When electrons are oxidized, they are lost, and when they are reduced, they are gained.

How to balance HCl + Fe2S3?

Following are the steps to balance the reaction mixture of (HCl + Fe2S3):

Step 1: Calculating the number of atoms in reactants and products

The first step in determining the number of atoms involved in reactants and products is to determine how many atoms are involved in each. According to the general equation, in reactants 1H, 2Fe, and 3S there is an increase in mass. There are 2H, 2S, 1Fe, and 2Cl in the product. 

HCl + Fe2S3 = FeCl2 + H2S + S

Step 2: Comparing the number of molecules in reactants and products

In HCl-Fe2S3, the atoms or molecules are arranged in the same way. The first attempt at balancing has been made by multiplying 4 with HCl, 2 with H2S, and 2 with FeCl2

4HCl + Fe2S= 2H2S + S + 2FeCl2

Step 3: Calculate the coefficient

All variables and coefficients are calculated using the Gauss elimination method. This results in a coefficient of 4:1::2:1:2.

Step 4: Calculate the balanced chemical equation

In the final step, every element in the chemical equation is balanced, and when these elements are combined, the reaction occurs as follows: 

4HCl + Fe2S→ 2H2S + S + 2FeCl2

HCl + Fe2S3 titration

Below is the titration reaction between hydrochloric acid and iron(III) sulphide(Fe2S3):

4HCl + Fe2S3 → 2FeCl2 + 2H2S + S

Apparatus used

Pipette, burette clamp, rubber tube with a syringe connected, grease stand with pencil, different-sized beakers (250 ml-1, 100 ml-3), and a 250 ml flask.

Titrant and titre

After the titer was taken in a conical flask, the molecule was analysed as iron sulphate. The titration will use hydrochloric acid as the titrant is poured into the burette.


Phenolphthalein, often known as methyl orange, is an indicator that is green in basic pH and red in acidic pH.


  • 250 mL of a solution of hydrochloric acid should be made in a batch.
  • 100 mL of distilled water should be added to the solution to dilute it.
  • The mixture should be treated with drops of phenolphthalein or methyl orange solution.
  • The colour should initially change after titrating the iron(III) sulphide solution.
  • To get a reading, repeat the process three to four times.

HCl + Fe2S3 net ionic equation

Following are the steps involved in writing the Net ionic equation:

Step 1: Write the molecular equation in the balanced form:

4HCl + Fe2S3 → 2FeCl2 + 2H2S + S

Step 2: Assign state to each substance as either a solid(s), liquid(l), gas(g), or aqueous(aq):

4HCl(aq) + Fe2S3(s) → 2FeCl2(aq) + 2H2S(g) + S(s)

Step 3: Separate each ion:

H2S → It is in gaseous form

FeCl2 → Fe2+ + 2Cl

Fe2S3 2Fe2+ + 3S2-

HCl → H++ Cl

Step 4: Write the complete ionic equation:

2Fe3+(aq) + 3S2-(aq) + 6H+(aq) + 6Cl(aq) → 2Fe3+(aq) + 6Cl(aq) + 3H2S(s)

Step 5: Remove spectator ligand:

On both sides of the equation, Fe3+ and Cl act as spectator ions, which can be removed.

Step 6: The net ionic equation: 

3S2-(aq) + 6H+(aq) → 3H2S(s)

HCl + Fe2S3 conjugate pairs

  • In the reaction between iron sulphide and hydrochloric acid, the conjugate pair comprises the hydrochloric acid’s conjugate base and the corresponding salt’s conjugate acid.
  • Iron sulphide reacts with acids to form the conjugate acid H2S because it is a base.
  • Base Pairs of conjugates = HCl
  • Conjugate acid pair = H2S

HCl and Fe2S3 intermolecular forces

  • The intermolecular force between HCl and Fe2S3 is a dipole-dipole interaction or force of attraction.
  • Although HCl has two intermolecular forces—the London dispersion force and the dipole-dipole force, Dipole-dipole interactions have more force than the other. 
  • The H-Cl bond dipole generates the dipole-dipole forces because Cl is more electronegative than H.
  • Because HCl is polar, it interacts with other polar molecules through the dipole, Hδ+−Clδ−.

HCl + Fe2S3 reaction enthalpy

  • The reaction of Fe2S3 and hydrochloric acid has a -311.75 kJ/mol standard reaction enthalpy.
  • Hydrochloric acid with Fe2S3 typically reacts with a negative standard reaction enthalpy.
  • Mathematically,  δH = Hproducts – Hreactans = -ve

4HCl(aq) + Fe2S3(s) → 2FeCl2(aq) + 2H2S(g) + S(s)

ΔtH/ΔHf°= -928.4 kJ/mol -194.95kJ/mol – (-341.8 kJ/mol -29.83kJ/mol)

ΔtH/ΔHf°= -311.75 kJ/mol

Is HCl + Fe2S3 a buffer solution?

The reaction of hydrochloric acid with Fe2S3 is not a buffer reaction because buffer solutions don’t include strong acids or bases.

Is HCl + Fe2S3 a complete reaction?

The reaction between HCl + Fe2S3 can be regarded as complete due to the irreversibility of the reaction. As demonstrated in the following reaction, all of the reactant molecules will completely change into product molecules: 

4HCl + Fe2S3 → 2FeCl2 + 2H2S + S 

Is HCl + Fe2S3 an exothermic or endothermic reaction?

Fe2S3 and HCl result in Exothermic reactions because of the production of more stable product molecules and the release of heat in the form of energy.

Is HCl + Fe2S3 a redox reaction?

When HCl + Fe2S3 → FeCl2 + H2S + S, the reaction is redox in nature. Throughout the reaction, the components’ oxidation state stayed the same. It involves the exchange of electrons in redox reactions. Here, Fe is oxidised while H is reduced.

Fe + 2HCl → FeCl2 + H2

Is HCl + Fe2S3 a precipitation reaction? 

Iron(III)sulphide and hydrochloric acid do not precipitate in the reaction, which is known as  HCl + Fe2S3. This reaction does not result in a precipitate because iron(III) chloride is a soluble salt.

Is HCl + Fe2S3 reversible or irreversible reaction?

  • Iron(III)sulfide reacts irreversibly with hydrochloric acid because the reactant molecules undergo a displacement reaction, and the reaction cannot be reversed.
  • Displacement reactions are typically irreversible, in contrast to weak acid and base reactions.

Is HCl + Fe2S3 displacement reaction?

The reaction of HCl + Fe2S3 is known as a displacement reaction because the two reactant molecules exchange atoms throughout the encounter to form two completely different compounds. The Fe atoms are replaced by H atoms from HCl to form H2S, and when Cl atoms and Fe atoms combine to form FeCl2.


Iron(III) sulphide(Fe2S3) and hydrochloric acid(HCl) undergo a redox, displacement, and irreversible reaction. At room temperature, Fe2S3 decomposes into sulphur, hydrogen sulphide, and iron chloride. Chlorides are created using hydrochloric acid.

Monika Saini

Hi....I am Monika. I have done Masters in Chemistry. I am a Subject Matter Expert in Chemistry. I would say that I am a very passionate writer. The main goal of my writing is to present new perspectives. I want to discover new things that I can apply to my surroundings. Let's connect through LinkedIn-https://www.linkedin.com/in/monadbscr171291

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