15 Facts on HCl + MgCO3: What, How To Balance & FAQs

The reaction of colourless HCl acid solution and MgCO₃ which is insoluble in water forms a colourless aqueous compound. Let us find out different relevant facts about the reaction.

Hydrochloric acid also referred to as muriatic acid, is a colourless solution categorized as a strong acid, prepared from hydrogen and chloride elements. Magnesium carbonate is an odorless compound present in form of a whitish bulky powder used as a dying agent in food, printing inks, etc.

In the article, we will discuss the reaction mechanism, balancing method, titration and reaction enthalpy.

What is the product of HCl and MgCO₃?

HCl reacts with MgCO3 to form Magnesium Chloride, with carbon dioxide and water as by-products, as shown in the following reaction:

MgCO₃ + 2HCl → MgCl₂ + CO₂ + H₂O

What type of reaction is HCl + MgCO₃?

HCl+ MgCO₃ is a neutralization reaction since the reaction of HCL and MgCO₃ leads to the formation of salt which is MgCl₂.

How to balance HCl + MgCO₃?

To balance a chemical reaction, the following steps are to be followed-

• Step 1: Write down the unbalanced chemical reaction.
• MgCO₃ + HCl → MgCl₂ + CO₂ + H₂O
• Step 2: Write down the number of moles of each element in the reactant side and product side, as tabulated below,

• Step 3: For a balance reaction, the number of moles of each element in the reactant side is equal to the number of elements in the product side, in this case, chlorine and hydrogen moles are unbalanced.
• Step 4: Multiply HCl with 2 on the reactant side, which balances the reaction.
• Step 5: Balanced chemical reaction-

HCl + MgCO₃ titration

Since MgCO₃ is insoluble in water, back titration is performed.

Apparatus

Beaker, volumetric flask, conical flask, burette, titrating stand, and measuring cylinder

Indicator

An acid-base indicator is used: Phenolphthalein

Procedure

• Weigh a known amount of MgCO₃ in a beaker and pour the liquid HCl acid into it. The mixture is thoroughly mixed and transferred in the volumetric flask. To make up the solution up to the mark, distilled water is added.
• From the flask, transfer 25ml of the solution to the conical flask using a measuring cylinder.
• Add 2 to 3 drops of phenolphthalein indicator.
• Titrate the solution against 0.1M NaOH, and continue it till the colour changes to light pink. For accurate results, repeat the procedure three times and note down the titration reading.
• Using N₁V₁=N₂V₂, concentration of MgCO₃ is determined.

HCl + MgCO₃ net ionic equation

• Step 1: Write the total ionic equation

• Mg²⁺⁽aq) +CO₃²⁻ (aq)+2H⁺(aq) +2Cl⁻(aq) →Mg²⁺(aq) +2Cl⁻(aq)+H₂O(ℓ)+CO₂(g)

• Step2: Cancel out the elements whose ions remain unchanged throughout the reaction

• Mg²⁺⁽aq) +CO₃²⁻ (aq)+2H⁺(aq) +2Cl⁻(aq) →Mg²⁺(aq) +2Cl⁻(aq)+H₂O(ℓ)+CO₂(g)

• Step3: The reaming equation is the net ionic equation

• CO₃²⁻ (aq)+2H⁺(aq)→ H₂O(ℓ)+CO₂(g)

HCl + MgCO₃ conjugate pairs

In conjugate acid-base pairs, there is always a chemical difference of one proton between them,

• For HCl, Cl^– is the conjugate base.
• For MgCO₃, CO₃^– is the conjugate base.
• For H₂O, OH^– is the conjugate base.

HCl and MgCO₃ intermolecular forces

HCl is a covalent compound, and London dispersion forces and dipole-dipole interaction takes place. MgCO₃ being an ionic compound, possess an electrostatic force of attraction.

HCl + MgCO₃ reaction enthalpy

Reaction enthalpy of HCl reacting with MgCO₃, is -50.4KJ/mol, calculated as follow:

• Step 1: Write down the enthalpy of each element present in the reactant side and product side as tabulated below

• Step 2: The change in enthalpy of the reaction is calculated as follows-

• Change in Enthalpy = (summation of enthalpies in product side) – (summation of enthalpies in reactant side)

• Enthalpy Change = [1*(-801.15) + 1*(-285.83) + 1*(-393.51)] – [2*(-167.15) + 1*(-1095.79)] = -50.7 KJ/mol.

Is HCl + MgCO₃ a buffer solution?

HCl+ MgCO₃ reaction is not a buffer solution due to the presence of the strong acid that is HCl.

Is HCl + MgCO₃ a complete reaction?

HCl+ MgCO₃ is a complete reaction since at equilibrium complete moles of reactant are consumed, producing the complete product

Is HCl + MgCO₃ an exothermic or endothermic reaction?

HCl+ MgCO₃ is an exothermic reaction, since the reaction enthalpy is -50.4KJ/mol, which is negative, thereby increasing the temperature.

Is HCl + MgCO₃ a redox reaction?

The HCl+ MgCO₃ reaction cannot be classified as a redox reaction, because there is no electron transfer taking place, that is the oxidation state of elements on the product side remains unchanged.

Is HCl + MgCO₃ a precipitation reaction?

The HCl+ MgCO₃ reaction is not a precipitate reaction, since the reaction yields, MgCO₃ which is a salt soluble in water; CO₂ which is a gas; and H₂O, so there is no precipitate formed in the reaction.

MgCO₃ + 2HCl → MgCl₂ + CO₂ + H₂O

Is HCl + MgCO₃ reversible or irreversible reaction?

HCl+ MgCO₃ is an irreversible reaction, due to the formation of a gas molecule on the product side, which increases entropy, which makes the product side more stable than the reactant side.

Is HCl + MgCO₃ displacement reaction?

HCl+ MgCO₃ is a double displacement reaction. The reaction of HCl and MgCO₃ results in the formation of entirely two different compounds by interchanging the anions and cations of the reactant side.

How to balance HCl + CaCO₃ + MgCO₃ = CO₂ + CaCl₂ + Mg(OH)₂?

• First, write the unbalanced equation –

• HCl + CaCO₃ + MgCO₃ = CO₂ + CaCl₂ + Mg(OH)₂

• Tabulate the number of moles of each element in the reactant and product side as follow:

• To balance the equation, multiply 2 with HCl on the reactant side and multiply 2 with CO₂ on the product side, which balances the reaction.
• Therefore, the balanced equation is –

• 2HCl + CaCO₃ + MgCO₃ = 2CO₂ + CaCl₂ + Mg(OH)₂

Conclusion

The reaction of HCl with MgCO₃ forms whitish magnesium chloride which has a variety of uses. It is used in fire extinguishers, disinfectants, flocculating agent etc. It is a double displacement, neutralization, exothermic reaction with -50.7 KJ/mol enthalpy change.