15 Facts on HCl + Mg3N2: What, How To Balance & FAQs

HCl is a strong halogen acid and Mg₃N₂ is a salt of magnesium metal. Let us elucidate how these two starting materials react to each other.

Hydrochloric acid, the aqueous solution of HCl gas, is one of the important mineral acids. Mg₃N₂ is an ionic compound comprised of Mg²⁺ cation and N^3- (nitride) anion. Magnesium nitride, which appears as a greyish-green powder is soluble both in acid and water.

In this article, we will shed light on the crucial features of the reaction between HCl and Mg₃N₂, such as the nature of the reaction, intermolecular forces, balancing the equation of the reaction, etc.

What is the product of HCl and Mg₃N₂

The products of HCl + Mg₃N₂ are magnesium chloride (MgCl₂) and ammonium chloride (NH₄Cl).

HCl  +  Mg₃N₂  =  MgCl₂  +  NH₄Cl

What type of reaction is HCl and Mg₃N₂

HCl + Mg₃N₂ does not fall under any type of reaction as mentioned below.

• HCl + Mg₃N₂ is not a neutralization reaction as HCl is acid but Mg₃N₂ is not a base.
• HCl + Mg₃N₂ is not a decomposition reaction as a single reactant is not decomposed into two simpler product molecules.
• HCl + Mg₃N₂ is not a combustion reaction as it does not involve oxygen as a reactant to produce CO₂ and H₂O.
• HCl + Mg₃N₂ is not a combination reaction as the two reactants are not combined together to form a single product.

How to balance HCl and Mg₃N₂

The balanced equation for the reaction HCl + Mg₃N₂ is,

8HCl  +  Mg₃N₂  =  3MgCl₂  +  2NH₄Cl

Below steps are necessary to follow to derive the balanced equation.

• The unbalanced equation is
• HCl  +  Mg₃N₂  =  MgCl₂  +  NH₄Cl
• Check the number of atoms for the elements present here; H, Cl, Mg, and N before and after the reaction.

Elements	Before reaction	After reaction
H	1	4
Cl	1	3
Mg	3	1
N	2	1

• Multiple MgCl₂ by 3 so that number of atoms of Mg atom is 3 on both sides.
• Multiple NH₄Cl by 2 so that number of atoms of N atom is 2 on both sides.
• HCl  +  Mg₃N₂  =  3MgCl₂  +  2NH₄Cl  
• Again check the number of atoms of the other two elements H and Cl on both sides.

Elements	Before reaction	After reaction
H	1	8
Cl	1	8
Mg	3	3
N	2	2

• Multiple HCl by 8 so that number of atoms of H and Cl atoms is 8 on both sides.

• Thus the balanced equation is

• 8HCl  +  Mg₃N₂  =  3MgCl₂  +  2NH₄Cl

HCl and Mg₃N₂ titration

By performing back titration using an excess amount of HCl, the amount of Mg₃N₂ can be determined.

Apparatus

Measuring cylinder, conical flask, volumetric flask, titration stand, burette, and pipette.

Indicator

Phenolphthalein indicator is used in this titration method.

Procedure

• Take Mg₃N₂ in a conical flask and add excess HCl of known concentration and volume with the help of a pipette.
• Swirl it properly for some time, followed by adding a few drops of phenolphthalein.
• Titrate the unreacted acid left after a complete reaction with NaOH solution of known concentration using a burette.
• Continue the method until the color changes to light pink.
• Take the average burette reading after doing the titration 2-3 times.
• Using the formula S1V1 = S2V2, the amount of unreacted HCl is found.
• The amount of HCl reacted with Mg₃N₂ is obtained by subtracting the amount of unreacted HCl from the total HCl amount.
• Finally, the amount of Mg₃N₂ can be determined from the amount of HCl reacted with Mg₃N₂.

HCl and Mg₃N₂ net ionic equation

For HCl + Mg₃N₂, the net ionic equation is

8H⁺ (aq) + 2N³⁻ (aq)  =   2NH₄⁺ (aq)

The above equation is acquired by following the steps below.

• The complete ionic equation is
• 8H⁺ (aq) + 8Cl^– (aq) + 3Mg²⁺ (aq)  + 2N³⁻  (aq)   =   3Mg²⁺ (aq)  + 6Cl^– (aq) + 2NH₄⁺ (aq) + 2Cl^– (aq)
• Cancel the spectator ions (Cl^– and Mg²⁺) from both sides.
• The net ionic equation is
• 8H⁺ (aq) + 2N³⁻ (aq)  =   2NH₄⁺ (aq)

HCl and Mg₃N₂ conjugate pairs

For HCl + Mg₃N₂, the conjugate pairs are

• The conjugate pair of HBr is Br^–.
• The conjugate pair of Mg₃N₂ is not possible as it is a salt.

HCl and Mg₃N₂ intermolecular forces

For HCl + Mg₃N₂, the intermolecular forces present are

• HCl has two intermolecular forces; London dispersion forces and dipole-dipole interaction, of which the second one is vital because of its polar nature.
• Mg₃N₂ has electrostatic force of attraction because of its ionic nature.

HCl and Mg₃N₂ reaction enthalpy

For HCl + Mg₃N₂, the reaction enthalpy is -770.9 kJ/mole which is calculated as follows.

Compounds	Enthalpy of formation (kJ/mole)
HCl (aq)	-167.2
Mg3N2 (aq)	-881.6
MgCl2 (aq)	-796.9
NH4Cl (aq)	-299.7

• Reaction Enthalpy = ΣΔH_f°(products) – ΣΔH_f° (reactants) 
• = [3*(-796.9) + 2*(-299.7))] – [8*(-167.2) + (-881.6)] KJ/mol
• = -770.9 KJ/mol

Is HCl and Mg₃N₂ a buffer solution

HCl + Mg₃N₂  cannot form a buffer solution as HCl is a strong acid and Mg₃N₂  does not contain a conjugate base of the acid.

Is HCl and Mg₃N₂ a complete reaction

HCl + Mg₃N₂  is a complete reaction,  as after the formation of MgCl₂ and NH₄Cl, no other reactions occur.

Is HCl and Mg₃N₂ an exothermic or endothermic reaction

HCl + Mg₃N₂  is exothermic as heat is generated during the reaction.

Is HCl and Mg₃N₂ a redox reaction

HCl + Mg₃N₂  is not a redox reaction as the oxidation states of all the atoms present in the reactant and product molecules are intact.

H⁺¹Cl^-1  +  Mg₃⁺²N₂^-3   =    Mg⁺²Cl₂^-1  +  N^-3H₄⁺¹Cl^-1 

Is HCl and Mg₃N₂ a precipitation reaction

HCl + Mg₃N₂  is not a precipitation reaction as both the products MgCl₂ and NH₄Cl are water-soluble compounds.

Is HCl and Mg₃N₂ reversible or irreversible reaction

HCl + Mg₃N₂  is an irreversible reaction as it is a unidirectional reaction.

Is HCl and Mg₃N₂ displacement reaction

HCl + Mg₃N₂  is not a displacement reaction as cations or anions are not swapped between the two compounds.

Conclusion

To conclude, the product MgCl₂ is the chloride salt of the magnesium ion. The solution of the other product NH₄Cl is mildly acidic as it is a salt of a weak base and strong acid. The compound is an important source of nitrogen supply in fertilizers.