15 Facts on HBr + CH3NH2: What, How To Balance & FAQs

The reaction between HBr (Hydrobromic acid) and CH₃NH₂ (Methylamine) is a simply acid-base reaction. Let us see how HBr and CH₃NH₂ react with each other.

HBr+CH₃NH₂ is a neutralization reaction between a strong hydrobromic acid and a weaker base methyl amine. HBr is a strong acid compared to its counterpart, HCl (Hydrochloric acid), but weaker than HI (Hydroiodic acid), a known stronger mineral acid, whereas CH₃NH₂, because of its organic nature, becomes a weak base.

This article discusses various facts about HBr + CH₃NH₂ reaction like the product, type, enthalpy, conjugate pairs of the reaction and many more.

What is the product of HBr and CH₃NH₂

Methylammonium bromide salt was obtained as product from the reaction between HBr and CH₃NH₂ in an aqueous solution.

CH₃NH_2(aq) + HBr_(aq) = CH₃NH₃Br _(aq)

What type of reaction is HBr + CH₃NH₂ ?

Reaction between CH₃NH₂ and HBr is a weak base–strong acid reaction, also known as a neutralization reaction which leads to salt formation.

How to balance HBr + CH₃NH₂ ?

Balanced equation of the HBr + CH₃NH₂ is,

CH₃NH_2(aq) + 3HBr_(aq) = CH₃NH₃Br _(aq)

HBr + CH₃NH₂ Titration

HBr + CH₃NH₂ titration is a weak base-strong acid titration.

Apparatus used –

• Burette
• Burette stand
• Clamps
• Conical flask
• Beaker
• Measuring cylinder
• dropper

Chemicals and Indicator used

• Standard aqueous solution of CH₃NH₂
• Given normality aqueous HBr solution
• Methyl orange as an indicator

Procedure

1. Fill the burette up to the mark with a standardized aqueous solution of methylamine (Weak Base), and clamp the burette to the burette stand.
2. Take 25 ml of HBr solution (Strong acid) in a conical flask with the help of a measuring cylinder. Add 2-3 drops of methyl orange indicator, which gives red/orange color to the solution.
3. Add the burette solution dropwise to the conical flask with constant stirring until the red/orange color changes to pale yellow.
4. Note down the burette reading, which is called as an endpoint of the titration, as, at this point, the amount of moles of acid and base react are same.
5. Repeat the same procedure twice. Take the average burette reading for further calculation.
6. Now, using the M₁V₁= M₂V₂ formula, we can calculate the molarity and normality of HBr.
   • M₁ – Molarity of standardized aqueous solution of methylamine
   • M₂ – Molarity of given HBr
   • V₁ – Initial burette reading volume
   • V₂ – Final burette reading (Average)

HBr + CH₃NH₂ Net Ionic Equation?

The complete ionic equation of the reaction between HBr + CH₃NH₂ is as follows.

CH₃NH_2(aq) + H⁺_(aq) + Br^–_(aq) = CH₃NH₃Br _(aq)

As HBr is a strong mineral acid in this equation, it dissociates completely in an aqueous solution. Br^– anion is common on both sides, so it gets canceled out and which gives a net ionic equation as follows,

CH₃NH_2(aq) + H⁺_(aq) = CH₃NH₃⁺ _(aq)

HBr + CH₃NH₂ Conjugate pairs

Conjugate pairs of HBr and CH₃NH₂ are as follows,

• The Conjugate base pair of HBr is Br^–. When HBr gets dissociated in water gives a proton to H₂O and releases Br^– ion.
• The Conjugate acid pair of CH₃NH₂ is CH₃NH₃⁺.

HBr and CH₃NH₂ Intermolecular forces

There are three types of bonds between the reactant molecules, as follows,

• Dipole-Dipole Forces – Due to the polar nature of the molecules, both HBr and CH₃NH₂ possess dipole-dipole interaction between molecules.
• London dispersion Forces – In addition to the abovementioned interaction, the HBr and CH₃NH₂ also has dispersion forces working on the molecules.
• Hydrogen bonding – Stronger than all the above forces, HBr and CH₃NH₂ also posses intermolecular hydrogen bonding. The presence of water mediates stronger intermolecular hydrogen bonding between the molecules. Dotted line in following figure shows intermolecular hydrogen bonding.

HBr + CH₃NH₂ reaction Enthalpy

The bond Enthalpy of the reaction can be calculated by subtracting the bond enthalpy (Enthalpy of formation ∆_f H) of reactants from the bond enthalpy of product.

CH₃NH_2(aq) + HBr_(aq) = CH₃NH₃Br _(aq)

Is HBr + CH₃NH₂ a Buffer solution?

An aqueous solution of HBr + CH₃NH₂ does not form a buffer solution because of the strong acidic nature of HBr.  As a buffer solution is a combination of weak acid-base conjugate pairs, which is meant to resist any changes in the pH of the solution. But in this case this solution can not maintain the pH of solution.

Is HBr + CH₃NH₂ a Complete reaction?

HBr + CH₃NH₂ is a complete reaction as the formation of a stable product, i.e., methylammonium bromide, takes place. Also, this is a neutralization reaction where the equilibrium is reached, i.e., concentrations of reactant and products will remain unchanged after the completion of the reaction.

Is HBr + CH₃NH₂ an Exothermic or Endothermic reaction?

The reaction between HBr and CH₃NH₂ is Exothermic as the Bond enthalpy of the reaction (∆H) is negative.

Is HBr + CH₃NH₂ a Redox reaction?

HBr + CH₃NH₂ is not a redox reaction, as there is no change in the oxidation state of Nitrogen.

Is HBr + CH₃NH₂ a Precipitation reaction?

HBr + CH₃NH₂ is not a precipitation reaction as the product of this reaction, i.e., Methylammonium Bromide salt, is soluble in water. So, there is no precipitation occurs during the reaction.

Is HBr + CH₃NH₂ reversible or irreversible reaction?

The Bond Enthalpy (∆H) of HBr + CH₃NH₂ is negative, which indicates that the reaction is exothermic and irreversible.

Is HBr + CH₃NH₂ Displacement reaction?

HBr + CH₃NH₂ is not a displacement reaction, as there is no displacement; instead, an addition reaction takes place, which gives a salt methylammonium bromide.

Conclusion

HBr+CH₃NH₂ is a strong acid-weak base neutralization reaction, leads to a stable product, i.e., methyl ammonium bromide salt formation. This is an exothermic, irreversible reaction, and the aqueous solution of this reactant can not form a buffer solution. Also contain strong intermolecular Hydrogen-bonding.