15 Facts on HBr + MgO: What, How to Balance & FAQs

Hydrobromic acid (HBr) is one of the strongest mineral acids and Magnesium Oxide (MgO) is a basic oxide. Let us study the reaction of HBr+ MgO in detail.

HBr is produced by reacting Bromine gas, Sulfur dioxide and Water. HBr is participates in anti-Markovnikov hydrohalogenation (Markovnikov’s rule) of alkenes. MgO exists as a white solid mineral powder which hygroscopic in nature. MgO possesses high chemical and physical stability at high temperatures.

In this following article, we will learn some important aspects of HBr+ MgO such as balancing chemical equation, enthalpy, type of reaction in greater depth.

What is the product of HBr and MgO?

HBr+ MgO react to form Magnesium bromide (MgBr2) and Water. The chemical equation is as follows:

MgO + 2HBr => MgBr2 + H2O

What type of reaction is HBr + MgO?

The reaction of HBr+ MgO is acid-base neutralization reaction because HBr is a strong acid and MgO is a strong basic oxide which on reacting produce the respective salt and water.

How to balance HBr + MgO?

The unbalanced chemical equation for HBr+ MgO is

  • MgO + HBr => MgBr2 + H2O
  • The reaction of HBr+ MgO is balanced using following steps:
  • Firstly, note down the number of individual chemical species on the reactant side (LHS) and product side (RHS)
ElementNo. of atoms on reactant side (LHS)No. of atoms on product side (RHS)
Balancing chemical equation
  • Secondly, as per the number of species of LHS and RHS multiply by the appropriate stoichiometric coefficient. In this case HBr on LHS is multiplied 2.
  • The final balanced chemical equation is as follows:
  • MgO + 2HBr => MgBr2 + H2O

HBr + MgO titration

HBr+ MgO titration can be done in the following procedure,

Apparatus used

  • Burette
  • Pipette
  • Conical flask
  • Volumetric flask

Indicator used

  • Phenolphthalein indicator is used for this titration. It turns colorless in acidic solution while in basic solution it turns pink.


  • MgO is sparingly soluble in water and the direct titration is not feasible. Hence for the quantification ‘Back titration’ approach is convenient.
  • A known concentration of HBr and NaOH is prepared.
  • NaOH is taken as the burette solution.
  • In a conical flask, unknown amount of MgO is taken and dissolved in excess amount of HBr of known concentration
  • Phenolphthalein indicator is added (approximately 2-3 drops)
  • The solution in the conical flask is titrated against NaOH until the end point appears i.e., when the solution turns colorless to pink.
  • Amount of excess HBr can be calculated from the amount of NaOH consumed. Following formula is used-
  • VHBr* SHBr= VNaOH* SNaOH where (V is volume and S is concentration)
  • In this way, we can calculate the amount of HBr required for the neutralization MgO by the means of back calculation.

HBr + MgO net ionic equation

The net ionic equation of HBr+ MgO is

  • Mg2+(aq)+O2-(aq)+2H+(aq)+2Br(aq)=>Mg2+(aq)+2Br(aq)+H+(aq)+OH(aq)

HBr + MgO conjugate pairs

HBr+ MgO reaction has the following conjugate pairs,

  • The conjugate pair of HBr is Br (conjugate base) because HBr is a strong acid and donates a proton.
  • There’s no conjugate pair of MgO to exist due to it being a metal oxide.

HBr and MgO intermolecular forces

HBr+ MgO reaction has the following intermolecular classes,

HBr + MgO reaction enthalpy

The reaction enthalpy of HBr+ MgO is -91.94 kJ mol-1, which is due to the high enthalpy of hydration exhibited by Mg2+ ion.

Is HBr + MgO a buffer solution?

HBr+ MgO is not a buffer solution because HBr is a strong acid, and buffer requires a weak acid and its conjugate base to maintain the pH.

Is HBr + MgO a complete reaction?

HBr+ MgO is a complete reaction because it takes place in forward direction and no excess HBr or MgO remains as reactants.

Is HBr + MgO an exothermic or endothermic reaction?

HBr+ MgO is an exothermic reaction. The reaction enthalpy of the reaction is -91.94 kJ mol-1 . The negative value of enthalpy represents the release of energy in the form of heat during reaction, hence the reaction is exothermic in nature.

Is HBr + MgO a redox reaction?

HBr+ MgO is not a redox reaction because there is no change in the oxidation states of the ions involved.

Is HBr + MgO a precipitation reaction?

HBr+ MgO is not a precipitation reaction because the product formed MgBr2 gets dissolved in the water and acid quite easily.

Is HBr + MgO reversible or irreversible reaction?

HBr+ MgO is an irreversible reaction because it is unidirectional in nature.

Is HBr + MgO displacement reaction?

HBr+ MgO is a double displacement reaction because O2- is getting replaced by Br and Mg2+ by H+ to form MgBr2 as a salt and water.


Hydrobromic acid (HBr) and Magnesium oxide (MgO) react to form Magnesium bromide and water. HBr+ MgO is a typical acid-base neutralization reaction. Magnesium bromide is used as a catalyst in many reactions, tranquilizer, and a mild sedative.