15 Facts on HCl + MnO2: What, How To Balance & FAQs

Hydrochloric acid is a colorless solution with a distinctively pungent smell whereas MnO₂ has an asphalt odor. Let us read how HCl and MnO₂ react with each other.

Manganese dioxide is a blackish or brownish, inorganic compound, naturally occurring compound. It is used as a pigment and reagent in organic synthesis. MnO₂ has a molar mass of 86.9268 g/cm³. HCl is a very strong acid.

In detail, this article will inspect key features of the HCl and MnO₂ reaction, like products, net ionic equation, type of reaction, and intermolecular forces of interactions.

What is the product of HCl and MnO₂

Scacchite (MnCl₂), dichlorine (Cl₂), and water (H₂O) are products of the reaction HCl + MnO₂.

HCl +MnO₂ = MnCl₂ + Cl₂ + H2O

What type of reaction is HCl + MnO₂

The reaction type of HCl +MnO₂ is a redox reaction.

How to balance HCl + MnO₂

The overall balanced molecular equation for HCl +MnO₂ is –

4HCl +MnO₂ = MnCl₂+ Cl₂+ 2H₂O

The balanced equation is derived by using the following method:

• All the compounds of the reaction are labeled with a different variable.

• a MnO₂ + b HCl = c MnCl₂+ d Cl₂ + e H₂O

• Create a system of equations for each reactant and product side element.

• Mn = 1a+1c, O=2a+1e, H= 1b+2e, Cl = 1b=2c=2d

• By using the Gaussian elimination or substitution method, solve all equations for each variable.

• a= 1(MnO₂), b=2(HCl), c=1(MnCl₂), d=1(Cl₂), f=2(H₂O)

• Substitute for each of the coefficients.
• Thus, the balanced equation is as follows:

• 4HCl + MnO₂ = MnCl₂+ Cl₂ + 2H₂O

Is HCl + MnO₂ titration

Titration between HCl and MnO₂ is not feasible because of HCl, as due to its oxidizing property Cl₂ is liberated, which does not turn the medium into acidic. Whereas MnO₂ is a water-insoluble solid, which makes stirred titration mixture look like mud.

HCl + MnO₂ net ionic equation

The net ionic equation for HCl + MnO₂ is as follows;

2HCl + MnO₂ + 2H+ = Mn2+ + Cl₂ + 2H₂O

Following are steps to find the net ionic equation for the reaction.

• The given equation is –

• HCl(aq) + MnO₂ (s)= Mn²⁺(aq) + Cl₂(aq) 

• Mn oxidation number is decreased from +4 to +2. This implies that Mn is reduced.
• In Cl, it is oxidized because its oxidation number is increased from -1 to 0.
• Following are oxidation and reduction half-reactions of the given reaction-
• HCl =Cl₂ , MnO₂ =Mn²⁺
• Now, balance each element except H and O in the equation, and the equations become-
• 2HCl = Cl₂ , MnO₂ =Mn²⁺
• Now balance oxygen and hydrogen using water and proton on both sides, so the we get following equations –
• 2HCl = Cl₂ + 2H⁺
• MnO₂ + 4H⁺ = Mn²⁺ + 2H₂O
• By balancing charges on both sides we get equations as,
• 2HCl =Cl₂ + 2H⁺ + 2e^–       (i)
• MnO₂ + 4H⁺ + 2e^– = Mn²⁺ + Cl₂ + H₂O      (ii)
• Now add both the equations (i) and (ii), we get final net ionic equation as –
• MnO₂ + 2HCl +2H⁺ = Mn²⁺ + Cl₂ + 2 H₂O

HCl + MnO₂ conjugate pairs

The conjugate acid or base pairs of HCl + MnO₂ are-

• HCl (Conjugate base) = Cl ^–
• HCl (Conjuagte acid) = H₃O⁺
• MnO does not have conjugate pairs as it is an amphoteric oxide.

HCl + MnO₂ intermolecular forces

The different types of intermolecular forces or interaction involved in HCl + MnO₂ reaction are-

• In HCl, there are two types of intermolecular forces present, dipole-dipole interactions and London dispersion forces. Among these dipole-dipole interactions, forces are stronger.
• In MnO₂, strong ionic forces are present with high electrostatic forces.
• Water (H₂O) forms H- bonding.

HCl + MnO₂ reaction enthalpy

The reaction enthalpy of HCl + MnO₂ is +272.3 KJ/mol.

Molecules	Reaction enthalpy(KJ/mol)
MnO2	-520
HCl	-92.3
MnCl2	-481.2
H2O	-68
Cl2	0

• The total enthalpy of reaction = total of product enthalpy – total enthalpy of reactant
• Thus for the reaction- 4HCl + MnO₂ = MnCl2 + Cl₂ + 2H₂O
• (-369.3) + (- 520)= (- 481.2) + (- 136)
• (-889.3) = (- 617)
• Reaction enthalpy = (-617) – (-889.3)
• The total enthalpy of reaction= 272.3 KJ/mol

Is HCl + MnO₂ a buffer solution

HCl + MnO₂ when mixed does not form a buffer solution because of HCl; as it is a very strong acid, and generally buffer solutions are prepared from a weak acid and its respective conjugate base.

Is HCl + MnO₂ a complete reaction

The reaction between HCl + MnO₂ is a complete reaction, and the products (MnCl₂, Cl₂, and H₂O) so formed are not converted back to reactants, and further, there are no products formed.

Is HCl + MnO₂ an exothermic or endothermic reaction

The HCl + MnO₂ reaction is an endothermic reaction, as the total enthalpy of the reaction is positive (272.3 KJ/mol). 

Is HCl + MnO₂ a redox reaction

HCl + MnO₂ is a redox reaction as Mn⁴⁺ gets reduced to Mn²⁺, and 2Cl^– gets oxidized to 2Cl, where MnO₂ acts as an oxidizing agent, and HCl acts as a reducing agent.

Is HCl + MnO₂ a precipitation reaction

The reaction HCl + MnO₂ is an example of a precipitation reaction, as a brownish precipitate of MnCl₂ is formed at the end of the reaction.

Is HCl + MnO₂ reversible or irreversible reaction

HCl + MnO₂ is an irreversible reaction because chlorine gas (Cl₂) is evolved at the end of the reaction and thus the reaction cannot be reversed back.

Is HCl + MnO₂ displacement reaction

The HCl and MnO₂ reaction is a type of double-displacement reaction, because Mn displaces Cl from HCl, and O is displaced to H from MnO₂.

Conclusion

At last, when the reaction takes place between HCl and MnO₂ the products formed are MnCl₂, H₂O, and Cl₂. During this production of chlorine gas takes place at the end of the reaction. Manganese dioxide (MnO₂ ) is mainly used to manufacture dry-cell batteries.