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

by

The crux of a chemical reaction is the formation of specific products. Let us see how this reaction serves as an example.

HBr, a strong mineral acid in both aqueous and gaseous forms, is an important lab reagent in analytical chemistry and has a density of 1.49 g/cm3. KOH or caustic potash, is a strong base known for its corrosive nature and highly nucleophilic properties. The pH of 1M HBr is nearly zero while the pH of 1M KOH is 12-13.

This interesting article will delve into the combination of acid and base, typically dealing with intermolecular forces and reaction enthalpies.

What is the product of HBr and KOH?

HBr and KOH are reacted to form potassium bromide and water molecules respectively. The reaction occurs as:

  • KOH + HBr→ KBr + H2O

What type of reaction is HBr + KOH?

The reaction of HBr and KOH is an example of a neutralisation where an acid and base combine to give salt and water.

How to balance HBr and KOH?

The chemical equation is already balanced, keeping in mind the stoichiometry and do not need additional atoms.

  • KOH + HBr→ KBr + H2O

HBr + KOH Titration

HBr and KOH reaction is an acid-base colour based titration.

Apparatus

  • Graduated burette
  • Conical flask
  • Volumetric flask
  • Burette stand
  • Sample beakers

Titre and Titrant

  • KOH is used as the titrant, the substance added to the analyte.
  • HBr is the titrand or analyte, whose concentration is to be estimated.

Indicator Used

  • Phenolphthalein is a common dye indicator used in acid-base titrations. It becomes colourless in an acidic environment while turning pink in a basic environment.

Procedure 

  • The burette is washed and filled with standardised KOH solution and clamped to the stand.
  • In the conical flask, the acid solution of a specific volume is taken.
  • A few drops of the phenolphthalein indicator is mixed in the contents of the conical flask.
  • The titration process is carried out with repeated stirring.
  • The solution shall turn from colourless to pink at the end point when equal moles of acid and base have reacted.
  • The estimation of the acid is done by the formula:
  • VKOH SKOH = VHBr SHBr
Titra ch 1
Titration Setup

HBr+ KOH Net Ionic Equation

The steps to be followed to derive the net ionic equation are as follows:

  • H+(aq) + Br–(aq) + K+(aq) + OH–(aq) → K+(aq) + Br–(aq) + H+(aq) + OH‑(aq)
  • Hydrobromic acid gets dissociated into hydrogen and bromide ions in an aqueous solution.
  • Caustic potash gets dissociated into potassium and hydroxyl ions respectively.
  • KBr in the ionic form creates potassium and bromide ions respectively.
  • The water molecule dissociated into hydrogen and hydroxyl ions respectively.

HBr+ KOH Conjugate Pairs

The HBr and KOH reaction conjugate pairs, which differ by one proton, are derived as:

  • The conjugate base of HBr= Br–
  • The conjugate acid of KOH= K+
  • The conjugate base of H2O= OH–

HBr and KOH Intermolecular Forces

HBr and KOH reaction has the following conjugate pairs,

  • HBr is an ionic compound but in gaseous entities, there is a weak covalent bond between Hydrogen and Bromine.
  • KOH involves in strong H-bonding with electronegative atoms, even so with HBr.
  • Due to the highly polar nature of HBr, there exists strong ion-ion and ion-dipole interactions in HBr.
  • Water shows intermolecular H-bonding with significant Van der Waals forces.
  • KBr also shows an ionic bond and exists as a face-centred cubic lattice.
ElementElectronegativity Value
Potassium0.8
Hydrogen2.1
Bromine2.9
Oxygen3.5
Electronegativity Chart

HBr+ KOH Reaction Enthalpy

HBr and KOH reaction enthalpy is -172 kJ/mol. The enthalpy information is as follows:

  • Bond enthalpy of HBr = +366 kJ/mol
  • Bond enthalpy of KOH = +343 kJ/mol
  • Bond enthalpy of KBr = +383 kJ/mol
  • Bond enthalpy of H2O = +498 kJ/mol
  • Reaction Enthalpy of above reaction= (366 + 343) – (383 + 498)= -172 kJ/mol

Is HBr + KOH a Buffer Solution?

HBr and KOH reaction cannot produce a strong buffer solution as it contains a strong acid and strong base which cannot maintain the pH of a solution.

Is HBr + KOH a Complete Reaction?

HBr and KOH reaction is complete because,once equilibrium is reached, products are completely formed.

Is HBr + KOH an Exothermic Reaction?

HBr and KOH reaction is an exothermic reaction as the negative enthalpy indicates the system releases some heat in the surroundings.

Is HBr + KOH a Redox Reaction?

The reaction of HBr and KOH is not a complete redox reaction as the oxidation state in the products and reactants remains unchanged.

Is HBr + KOH a Precipitation Reaction?

HBr and KOH reaction is not a precipitation reaction as one of the products is water and other products is also formed in the solution phase.

Is HBr + KOH a Reversible Reaction?

HBr and KOH reaction is reversible in nature like most acid-base reactions as products can easily ionise if we alter the conditions and the system undergoes a backward reaction.

Is HBr + KOH a Displacement Reaction?

HBr and KOH reaction is an example of a double displacement reaction. The reaction occurs as:

  • KOH + HBr→ KBr + H2O
  • Potassium displaces the Hydrogen of the acid and forms a salt of a strong acid.
  • The hydrogen ions combine with the hydroxyl ions to form water molecules.

Conclusion

KOH is a white basic solid with huge applications as a food stabilizer and pH controlling agent. HBr is preferred in organic reactions as a good cleaving agent. Thus, this reaction is a prime example of a good acid-base titration and laboratory method to prepare KBr.