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

Hydrochloric acid is a strong acid, and Manganese oxide is a basic oxide. Let us learn how hydrochloric acid reacts with manganese oxide and generates products.

Hydrochloric acid (HCl) is generally occurring as a solution of hydrogen chloride in water. Manganese oxide consists of Mg2+ and O2- ions held by an ionic bond in a lattice. As the oxide ions are strongly bonded in the lattice, it appears as a mild basic oxide.

In this article, we will discuss how these two important chemicals react with each other and discuss some important questions.

What is the product of HCl and MgO?

HCl and MgO are reacted to form manganese chloride and water. The reaction equation is:

2HCl + MgO = MgCl2 + H2O

What type of reaction is HCl + MgO?

The reaction is an acid-base neutralization type of reaction. HCl and MgO are strong acids and basic oxides, respectively.

How to balance HCl + MgO?

Step 1:

Find the number of elements present in both sides of the reaction HCl + MgO = MgCl2 + H2O

  • Reactant side: 1 H, 1 Cl, 1 Mg, 1 O
  • Product side: 2H, 2 Cl, 1 Mg, 1 O

Step 2:

Observe how the number of elements can be matched on both sides. We can see if we increase the one molecule of HCl on the reactant side, the number of elements will be matched. Hence, the balanced equation will be:

2HCl + MgO = MgCl2 + H2O

HCl + MgO titration

Apparatus Used

  • Burette
  • Pipette
  • Conical flask
  • Volumetric flask


  • A phenolphthalein indicator is used in this reaction. It turns pink-violet in presence of the base and turns colourless in presence of acid.


  • Magnesium oxide is not very soluble in water and is difficult to titrate directly. But Its mass can be determined by using a ‘back titration‘ method.
  • A similar known concentration solution of HCl and NaOH is prepared.
  • The burette is loaded with the prepared NaOH solution.
  • In a conical flask, an unknown amount of magnesium oxide was dissolved entirely in an excess amount of prepared hydrochloric acid.
  • Two drops of Phenolphthalein are added to the flask.
  • The NaOH solution from the burette is allowed to be added to the conical flask. The appearance of a pink-violet colour confirms the endpoint.
  • The amount of excess HCl present in the flask is calculated from the amount of NaOH used using the VHClSHCl=VNaOHSNaOH formula (V=volume, S=concentration).
  • Therefore, the amount of HCl required for the neutralization of MgO can be calculated via back calculation.

HCl + MgO net ionic equation

The net ionic equation of HCl and MgO is: 2H++2Cl + Mg2++O2- = Mg2++2Cl + H++OH

HCl + MgO conjugate pairs

The conjugate pair of HCl is Cl. MgO does not have a conjugate pair as oxide, and O2- has no proton, so it has no conjugate base.

HCl and MgO intermolecular forces

As intermolecular forces, the dipole-dipole and London dispersion forces are present in the HCl and MgO. Between the two, the dipole-dipole forces are stronger.

HCl + MgO reaction enthalpy

The reaction enthalpy of the HCl + MgO reaction is −57.33 kJmol−1, Which is due to the very high enthalpy of hydration of Mg2+ion.

Is HCl + MgO a buffer solution?

As HCl is a strong acid, it can not form a buffer solution.

Is HCl + MgO a complete reaction?

HCl + MgO is a complete reaction and produces MgCl2 salt and water upon completion. There will be no excess HCl or MgO present after completion if equimolar HCl and MgO are used.

Is HCl + MgO an exothermic or endothermic reaction?

HCl + MgO is an exothermic reaction. The reaction enthalpy of this reaction is −57.33 kJmol−1. As the reaction enthalpy is negative, it releases heat during the reaction, and hence, it is exothermic in nature.

Is HCl + MgO a redox reaction?

HCl + MgO is not a redox reaction. There is no change in the oxidation state of the ions before and after the reaction.

Is HCl + MgO a precipitation reaction?

HCl + MgO is not a precipitation reaction, as no products precipitate out during the reaction.

Is HCl + MgO reversible or irreversible reaction?

HCl + MgO is an irreversible reaction. Because once MgCl2 and water are formed, we can not get back HCl and MgO.

Is HCl + MgO displacement reaction?

HCl + MgO is a double displacement type of reaction. Here O2- gets replaced by Cl to form the MgCl2 salt and water as the product.


Hydrochloric acid (HCl) and manganese oxide (MgO) reacts to form manganese chloride (MgCl2) and water. It is an acid-base neutralization type of reaction. MgCl2 can be absorbed very easily by our body and can be a source of manganese supplement.

Diptangshu Datta

Hello...I am Diptangshu Datta Mal. I have completed my PhD at Indian Institute of Technology (IIT) Kharagpur, India. Prior to that, I have completed my B.Sc. (Hons.) in chemistry from Vidyasagar University and my M.Sc. in Chemistry from the Indian Institute of Technology (IIT) Madras, India. With Lambda Geeks, I will try to contribute in whatever way possible to make chemistry and chemical concepts accessible to everyone in our community. You can reach me via Linkedin: https://www.linkedin.com/in/diptangshu-datta-mal-70a5a284/

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