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

MgCO₃, known as magnesium carbonate, is a metal salt, and HF (hydrogen fluoride) is a weak inorganic acid. Let us examine how they react to each other in detail.

MgCO₃ is an insoluble, odorless white solid that is majorly used to prepare magnesium oxide through the calcination process. HF is a highly corrosive acid with a pKa of 3.17 and is actively used as a fluorinating agent.

Here, we will study the reaction type, enthalpy, molecular forces, and the products associated with the reaction HF + MgCO₃.

What is the product of HF and MgCO₃

MgF₂ (magnesium fluoride), (CO₂) carbon dioxide gas, and water molecules are the products formed in the reaction HF + MgCO₃.

HF + MgCO₃ → MgF₂ + CO₂ + H₂O

What type of reaction is HF + MgCO₃

HF + MgCO₃ is a neutralization reaction as the acid HF neutralizes the base MgCO₃ to form the salt MgF₂. This reaction occurs in two steps,

• The first step is a displacement reaction.
• HF + MgCO₃ = MgF₂ + H₂CO₃
• In the next step, the decomposition of carbonic acid (H₂CO₃) takes place.
• H₂CO₃ = CO₂ + H₂O

How to balance HF + MgCO₃

HF + MgCO₃ is balanced using the below-listed steps

HF + MgCO₃ → MgF₂ + CO₂ + H₂O

• The elements present in each side of the equation are counted.

• In the next step, coefficients are added before the compounds to equate the number of elements on both sides. Before HF, a coefficient of 2 is added.

• Thus, the balanced equation is

• 2HF + MgCO₃ → MgF₂ + CO₂ + H₂O

HF + MgCO₃ titration

HF is titrated against MgCO₃ using a suitable indicator. This is an example of an acid (HF) and base (MgCO₃) titration.

Apparatus used

Burette, pipette, conical flask, measuring cylinder, funnel, volumetric flask.

Indicator

Phenolphthalein is used as the indicator.

H₂In (colorless in acidic medium) → In^2- (pink in basic)

Procedure

• Standard solution of HF is prepared and filled in the burette using a funnel.
• 10 ml of MgCO₃ solution is taken into a conical flask and to it, 2-3 drops of the indicator are added.
• HF is added dropwise from the burette into the conical flask with constant stirring.
• The colorless solution changes into light pink which marks the endpoint of the reaction.
• Three concordant readings are taken and used in calculating the concentration of the unknown MgCO₃ solution.
• The calculation is done using the formula N₁V₁ = N₂V₂.

HF + MgCO₃ net ionic equation  

The net ionic equation for HF + MgCO₃ is

2HF(aq) + MgCO₃(s)→ MgF₂(s)+ CO₂(g)+ H₂O(l)

The net ionic equation is deduced using the subsequent steps

• The balanced equation is written in the first step.
• 2HF + MgCO₃ → MgF₂ + CO₂ + H₂O
• The states (solid, liquid, gas, or aqueous) of the species involved in the reaction are indicated.
• 2HF(aq) + MgCO₃(s)→ MgF₂(s)+ CO₂(g)+ H₂O(l)
• The strong-electrolytes are split into ions in the next step. HF and H₂O are weak electrolytes so will not split.
• There is no strong electrolyte present in the equation. Thus, the net ionic equation is
• 2HF(aq) + MgCO₃(s)→ MgF₂(s)+ CO₂(g)+ H₂O(l)

HF + MgCO₃ conjugate pairs

HF + MgCO₃ is a conjugate pair as

HF + CO₃^2- = F^– + H₂CO₃

• F^– is the conjugate base of HF after giving H⁺.

• H₂CO₃ is the conjugate acid of the base CO₃^2-.

HF and MgCO₃ intermolecular forces

The intermolecular forces present in the reactants are,

• Ionic interactions are present between the molecules of MgCO₃.
• Hydrogen bonding and dipole-dipole interactions are present in HF molecules.

HF + MgCO₃ reaction enthalpy

HF + MgCO₃ reaction enthalpy is -55.9 KJ/mol. The enthalpy is calculated using the tabulated values and putting in the formula below,

• ∆H_f^°(reaction) = ∆H_f^°(products) – ∆H_f^°(reactants)
• = -1758.8 – (-1702.9) KJ/mol
• = -55.9 KJ/mol

Is HF + MgCO₃ a buffer solution

HF + MgCO₃ will form a buffer solution as HF is a weak acid and MgF₂ produced in the reaction is the conjugate salt of the acid HF.

Is HF + MgCO₃ a complete reaction

HF + MgCO₃ is a complete reaction because the products obtained are inert to each other and hence will not react further.

Is HF + MgCO₃ an exothermic or endothermic reaction

HF + MgCO₃ is an exothermic reaction as a large amount of heat is liberated during the reaction and the enthalpy has a negative value.

Is HF + MgCO₃ a redox reaction

HF + MgCO₃ is not a redox reaction as the oxidation state of the elements is same in both the reactants and the products.

Is HF + MgCO₃ a precipitation reaction

HF + MgCO₃ is a precipitation reaction as the salt (MgF₂) produced is insoluble in water and thus will form a precipitate.

Is HF + MgCO₃ reversible or irreversible reaction

HF + MgCO₃ is an irreversible reaction as the forward reaction is more favorable due to the increase in entropy attributed to the evolution of CO₂ gas.

Is HF + MgCO₃ displacement reaction

HF + MgCO₃ is a double displacement reaction as Mg is more reactive so it displaces hydrogen and forms MgF₂, whereas the H⁺ ion combines with carbonate ions to form H₂CO­₃.

HF + MgCO₃ = MgF₂ + H₂CO₃

Conclusion

The reaction is exothermic and occurs in an irreversible manner. MgCO₃ has wide applications in the food and cosmetic industry and is generally used as a laxative as well as a drying agent. MgF₂ is used in the manufacture of lenses and prisms as it is highly transparent over wide range of wavelengths.