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.
CH3NH2(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,
CH3NH2(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
- Fill the burette up to the mark with a standardized aqueous solution of methylamine (Weak Base), and clamp the burette to the burette stand.
- 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.
- Add the burette solution dropwise to the conical flask with constant stirring until the red/orange color changes to pale yellow.
- 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.
- Repeat the same procedure twice. Take the average burette reading for further calculation.
- 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.
CH3NH2(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,
CH3NH2(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.
CH3NH2(aq) + HBr(aq) = CH3NH3Br (aq)
Sr no. | Compound | No. of Moles | Bond Enthalpy (∆f H = KJ/mol at 298K) |
---|---|---|---|
1 | CH3NH2 | 1 | -21.05 |
2 | HBr | 1 | 366 |
3 | CH3NH3Br | 1 | -258 |
∆H = ∆f H (Product) -∆f H (Reactant)
= -258 – [(-21.05) + 366]
= -602.95 KJ/mol
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.
Hello…I am Neha, earned a doctorate degree in Chemistry from the Indian Institute of Science Education and Research Pune (IISER Pune). I have 1+ year of post-doctoral research experience from IIT Bombay and IISER Pune. Also worked in the industry as Senior Research Associate. My research focused on organometallic chemistry, material chemistry so on. Currently, working as a chemistry Subject Matter Expert. Apart from Chemistry, I like listening to music and singing songs, playing games, traveling, etc.
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