15 Facts on HCl + Ca(OH)2: What, How To Balance & FAQs

Calcium hydroxide has a basic property and can easily react with a strong acid like hydrochloric acid. Let us see the chemical behaviour of the reaction between HCl and CaOCl2.

An aqueous solution of hydrogen chloride is hydrochloric acid (HCl), often called muriatic acid. Hydrochloric acid is highly soluble in water. Calcium hydroxide (Ca(OH)2) is a white solid at room temperature that is only slightly soluble in water. When Ca(OH)2 and HCl react, a weak base-strong acid reaction occurs.

In this article, we shall discuss some of the properties of this reaction, like its product, type of reaction, enthalpy, and intermolecular forces, in detail.

What is the product of HCL and CA(OH)2 ?

When calcium hydroxide Ca(OH)2 and hydrochloric acid (HCl) combine, calcium chloride (CaCl2) and water are produced (H2O), when the reaction occurs, a colourless solution is produced after the white precipitate has dissolved.

Ca(OH)2 (s)+ 2HCl (aq) → CaCl2 (aq) + 2H2O (l)

What type of reaction is HCL + CA(OH)2 ?

The reaction between hydrochloric acid (HCl) and calcium hydroxide Ca(OH)2 is an acid-base reaction. It can also be categorised as a neutralisation reaction since acid and alkali have reacted from salt and water. 

How to balance HCL + CA(OH)2 ?

Step 1: Writing the general equation

The general equation is Ca(OH)2 (s)+ HCl (aq) → CaCl2 (aq) + H2O (l) 

Step 2: Arranging the similarity between the reactant and product

In the reaction, the number of moles of reactant must be equal to the number of moles of the product and the reaction have balanced moles.

Since the product has 2 moles of Cl atom. 2 moles of HCl are added. On the reactant side, there are 2 moles of oxygen. Thus, 2 moles of H2O are added on the product side.

Step 3: Writing the balanced equation

After adding the required number of moles on the reactant and product side, the overall balanced reaction is given by:

Ca(OH)2 (s)+ 2HCl (aq) → CaCl2 (aq) + H2O (l)

HCL + CA(OH)2 titration

An acid-base titration between calcium hydroxide and hydrochloric acid can be performed to measure the amount of calcium. Various conditions and apparatus are used, which are explained below.

Apparatus used

Burette, pipette, conical flask, burette holder, wash bottle, dropper, volumetric flask and beakers.

Titer and titrant

Hydrochloric acid is used as the titrant and filled in the burette. The chemical compound will be analysed with calcium hydroxide as the titer was taken in a conical flask.


Phenolphthalein is an acid-base indicator used to detect the end point of the titration.


  1. Standardised HCl was taken in a burette, and the given calcium hydroxide was taken in a conical flask.
  2. Added 1-2 drops of phenolphthalein indicator.
  3. Added HCl from the burette slowly into the conical flask with constant swirling until the solution turned from colourless to light pink.
  4. Repeated the procedure to get 3 concordant readings.

HCL + CA(OH)2 net ionic equation

Since the reaction between calcium hydroxide Ca(OH)2 and hydrochloric acid (HCl) is a neutralisation reaction, the net ionic reaction follows a neutralisation reaction which is as follows:

H+ (aq) + OH (aq) → H2O (l)

HCL + CA(OH)2 conjugate pairs

The conjugate pair of the reaction between hydrochloric acid and calcium hydroxide is as follows:

HCl   + OH →  Cl     + H2O

(Acid) (Base)    (Base)  (Acid)                  

In this reaction, HCl and Cl  are conjugate acid-base pairs and OH and H2O are another conjugate acid-base pair.

HCL and CA(OH)2 intermolecular forces

  • In HCl, dipole-dipole interactions and London dispersion intermolecular forces are the intermolecular forces that hold the hydrogen and chloride ions together.
  • Ca(OH)2 is an ionic compound with strong electrostatic attraction forces between Ca2+ and OH ions.

HCL + CA(OH)2 reaction enthalpy

The standard reaction enthalpy of the reaction between hydrochloric acid and calcium hydroxide is negative.

Energy profile diagram for an exothermic reaction

Is HCL + CA(OH)2 a buffer solution ?

HCl + Ca(OH)2 pairs of solutes would not form a strong buffer solution since HCl is a strong acid, not a weak acid. The acid should be weak, so adding more acid does not significantly change the pH.

Is HCL + CA(OH)2 a complete reaction ?

The above reaction is incomplete since there is no product formation. We can only determine whether or not the reaction will be complete once we observe any product on the right-hand side.

Is HCL + CA(OH)2 an exothermic or endothermic reaction ?

The reaction between hydrochloric acid and calcium hydroxide is exothermic. Therefore, this heat will be a driving force to complete the reaction.

Is HCL + CA(OH)2 a redox reaction ?

HCl + Ca(OH)2  is not a redox reaction since there is no change in the oxidation state of reactants and products.

Is HCL + CA(OH)2 a precipitation reaction ?

HCl + Ca(OH)2  is not a precipitation reaction. HCl is an aqueous solution, whereas Ca(OH)2 is a white precipitate. When a reaction occurs, a colourless solution is produced after the white precipitate has dissolved.

Is HCL + CA(OH)2 reversible or irreversible reaction ?

The reaction between calcium hydroxide Ca(OH)2 and hydrochloric acid (HCl) is irreversible because the products formed don’t react together to reform reactants.

Is HCL + CA(OH)2 displacement reaction ?

The above reaction is a double displacement reaction because the cations and anions swap to create the water and the salt.


This article summarises the reaction of HCl + Ca(OH)2 as a type of acid-base neutralisation reaction.

Mansi Kapoor

Hello everyone, I am Mansi Kapoor. I am a Postgraduate in Chemistry from the University of Delhi and have working experience as an SME in Chemistry. By sharing the University of Delhi's tradition of excellence, I am committed to doing better for the world through research, education, and community efforts. Let's connect through LinkedIn: https://www.linkedin.com/in/mansi-kapoor-92bb811b6

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