# 15 Facts on HBr + Mg3P2: What, How To Balance & FAQs

Magnesium phosphide (Mg3P2) is a salt composed of three Mg metals and two P non-metals. Hydrogen bromide (HBr) is a strong acid. Let us examine the reaction of HBr and Mg3P2.

Magnesium phosphide is a white crystalline cubic solid. It ignites on contact with air and reacts intensely with water. It is a strong reducing agent and is primarily used as a fumigant in agriculture. HBr is a pungent acid and a strong oxidizing agent used in producing organobromides.

In this article, we discuss various facts and FAQs on HBr + Mg3P2 chemical reaction, the type of reaction, the product formed, reaction enthalpy, etc.

## What is the product of HBr and Mg3P2?

HBr reacts with magnesium phosphide to form magnesium bromide (MgBr2) along with the evolution of phosphine (PH3) gas.

6HBr + Mg3P2 —–> 3MgBr2 + 2PH3

## What type of reaction is HBr + Mg3P2?

The reaction of HBr + Mg3P2 is an example of a double displacement reaction, also known as a salt metathesis reaction.

## How to balance HBr + Mg3P2?

The steps to balance HBr + Mg3P2 are as follows –

• Assign an alphabet to each compound in the reactant and product in order to represent the unknown coefficients.
• a HBr + b Mg3P2 —–> c MgBr2 + d PH3
• Generate an equation by summing all the coefficients of each element involved in the reaction.
• H → a=3d, Br → a=2c, Mg → 3b=c, P → 2b=d
• Apply the Gaussian elimination approach to determine the values of each assigned coefficient.
• The value of coefficients obtained after simplification is a= 6, b=1, c=3, d=2.
• The overall balanced equation is –
• 6HBr + Mg3P2 —–> 3MgBr2 + 2PH3

## HBr + Mg3P2 titration

HBr + Mg3P2 titration is generally avoided as their reaction is vigorous in nature with the liberation of toxic phosphine gas.

## HBr + Mg3P2 net ionic equation

The net ionic equation between HBr+ Mg3P2 is:

6H+ (aq) + Mg3P2 (s) = 3Mg2+ (aq) + PH3 (g)

The net ionic equation is derived by the following steps:

• Write the balanced equation indicating the physical states of each molecule.
• 6HBr (aq) + Mg3P2 (s) = 3MgBr2 (aq) + 2PH3 (g)
• Write the ionic form of soluble electrolytes that are present in the reaction. Hence, the complete ionic equation is –
• 6H+ (aq) + 6Br (aq) + Mg3P2(s)  =  6Mg2+ (aq) + 6Br (aq) + PH3 (g)
• Finally, to get the net ionic equation, cancel the spectator ions (6Br) on either side of the reaction.
• 6H+ (aq) + Mg3P2 (s) = 3Mg2+ (aq) + PH3 (g)

## HBr + Mg3P2 conjugate pairs

• HBr is a strong acid with Bras its conjugate base.
• There is no conjugate pair Mg3P2 as it is moisture-sensitive.

## HBr + Mg3P2 reaction enthalpy

HBr + Mg3P2 reaction enthalpy is -399.34 KJ/mol. The enthalpy of formation values is given below –

• ∆Hf°(reaction) = ∆Hf°(products) – ∆Hf°(reactants)

= -515 – (-115.66)

= -399.34 KJ/mol

## Is HBr + Mg3P2 a buffer solution?

HBr + Mg3P2 is not a buffer solution, as HBr is a strong acid, and Mg3P2 is an inorganic salt that can neither form a buffer solution nor maintain the pH level of other solutions.

## Is HBr + Mg3P2 a complete reaction?

HBr + Mg3P2 is a complete reaction, as water-soluble magnesium bromide salt is formed along with phosphine gas.

## Is HBr + Mg3P2 an exothermic reaction?

HBr + Mg3P2 is an exothermic reaction, as tremendous heat is expelled along with the evolution of phosphine gas.

## Is HBr + Mg3P2 a redox reaction?

HBr + Mg3P2  is not a redox reaction, as no transfer of electrons occurs within the reaction. Moreover, there is no change in the oxidation state of any element in HBr + Mg3P2 reaction; thus, it is not a redox reaction.

## Is HBr + Mg3P2 a precipitation reaction?

HBr + Mg3P2 is not a precipitation reaction as the product (MgBr2) formed during the chemical reaction is an electrically neutral salt, soluble in water.

## Is HBr + Mg3P2 an irreversible reaction?

HBr + Mg3P2 is an irreversible reaction since the reaction can never attain equilibrium due to the evolution of phosphine gas.

## Is HBr + Mg3P2 a displacement reaction?

HBr + Mg3P2 is a double displacement reaction because the more reactive magnesium displaces hydrogen from HBr, while H combines with the non-metal P to form PH3.

#### Conclusion

Magnesium phosphide is a binary alkali metal salt, mildly soluble in acids. MgBr2 formed in this reaction, is mainly used as a tranquilizer and as a catalyst in organic compound synthesis. PH3 is used in the fumigation of food grains.