15 Facts on HCl + K2O: What, How To Balance & FAQs

The formation of salts is an interesting way to understand the chemistry of acids and bases. Let us if this reaction provides us with such example.

Hydrochloric acid can exist in both liquid and gaseous (hydrogen chloride) forms.Potassium oxide is a famous yellow reagent having an antifluorite crystal lattice. It reacts vigorously in water to produce potassium hydroxide. The reaction should be performed with caution.

Let us see how the reaction of these two compounds happens, with their properties in this article.

What is the product of HCl and K2O?

HCl and K2O are reacted to form Potassium Chloride and Water respectively. The reaction equation is:

  • K2O + 2HCl =  2KCl + H2O

What type of reaction is HCl + K2O?

The reaction of HCl with K2O is a neutralisation reaction as a salt is produced in the solution.

How to balance HCl and K2O?

The steps to equate the above reaction scheme are as follows:

  • K2O+ HCl =  KCl + H2O
  • As both sides should be equal in atoms, keeping stoichiometry in mind, multiply KCl with 2 to equal with the Potassium atoms of K2Cr2O7.
  • K2O+ HCl =  2KCl + H2O
  • Multiply HCl with 2 as the product side has two hydrogen atoms.
  • K2O+ 2HCl =  2KCl + H2O

HCl + K2O Titration

The titration of HCl with K2O will yield significant results if a suitable indicator is used.


  • Graduated burette
  • Conical flask
  • Volumetric flask
  • Burette stands

Titre and Titrant

  • HCl is used as the titrant, the substance to be analysed.
  • K2O is the titre, the concentration of which is known.

Indicator Used

Phenolphthalein, a dye indicator is used in such acid-base titrations. It becomes colourless in acidic medium while turning pink in a basic medium.


  • Potassium oxide sample is weighed, taken in flask and dissolved in water to form a potassium hydroxide solution of known concentration.
  • The burette is filled with the above solution and clamped to the stand.
  • In the conical flask, HCl is taken whose concentration is unknown.
  • As the stopcock is loosened, drops of K2O solution fall inside the conical flask.
  • A drop of Phenolphthalein indicator is added soon to indicate the results.
  • At the endpoint, the solution turns from colourless to pale pink, indicating complete neutralisation.
  • Repeat the process twice to get better readings.
  • The unknown concentration of HCl is measured using the universal formula,
  • VK2O  SK2O = VHCl SHCl
Sample setup of Titration

HCl + K2O Net Ionic Equation

In HCl and K2O reaction, the solution of potassium and chloride ions are in an aqueous medium.

  • K2O(s) + 2HCl(aq) =  2K+(aq) +  2Cl(aq) + H+(aq) + OH(aq)

HCl + K2O Conjugate Pairs

Conjugate acid-base pairs refer to those pair of compounds that are differed by just one proton. For example,

  • HCl conjugate base (remove proton) = Cl
  • H2O conjugate base (remove proton) = OH

HCl and K2O Intermolecular Forces

HCl shows ionic character in an aqueous medium. Potassium chloride shows ion-dipole interactions with water and is polar in nature.

ElementElectronegativity Value
Electronegativity Values of Elements
KCl Bonding

HCl + K2O Reaction Enthalpy

Reaction Enthalpy of HCl and K2O reaction is -614 kJ/mol. The enthalpy information is given below:

  • Enthalpy of Formation of K2O = -363.2 kJ/mol
  • Enthalpy of Formation of HCl = -92.3 kJ/mol
  • Enthalpy of Formation of H2O = -285.8 kJ/mol
  • Enthalpy of Formation of KCl = -438 kJ/mol

Is HCl + K2O a Buffer Solution?

A strong buffer solution is not possible as it contains a strong acid like hydrochloric acid which does not maintain the pH of the system.

Is HCl + K2O a Complete Reaction?

The HCl and K2O reaction is complete as products can no more form once we reach an equilibrium.

Is HCl + K2O an Exothermic Reaction?

HCl and K2O reaction is exothermic as the reaction enthalpy is negative and neutralisation reactions generally release lots of heat.

Is HCl + K2O a Redox Reaction?

The HCl and K2O reaction of HCl and K2O cannot be termed redox as there is no change in oxidation state of an atom in the reactant and products.

Is HCl + K2O a Precipitation Reaction?

HCl + K2O is not a precipitation reaction as no precipitate is observed in the solution.

Is HCl + K2O a Reversible Reaction?

The HCl and K2O reaction is not reversible as complete products are formed which cannot be reverted unless we change the temperature and pressure conditions drastically.

Is HCl + K2O a Displacement Reaction?

The reaction of HCl with K2O is a double displacement or salt metathesis reaction as oxygen gets displaced by chlorine to form the salt.


The reaction of HCl with K2O forms whitish potassium chloride, dubbed as potash commercially, which has medicinal applications in prescribed amounts. The reaction serves as a good neutralisation reaction and even better as pH-metric titration.

Neeloy Bhattacharya

Hello....Neeloy here! I have pursued a Master' in Chemistry and am currently a Subject Matter Expert in this community. Science and reasoning feed my curiosity and I love to express whatever I see, in my words. Quiz addict. Let's connect at LinkedIn: www.linkedin.com/in/neeloy-bhattacharya-here

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