Calcium hydroxide and Hydrochloric acid Reaction | Ca(OH)2 + HCl

Calcium hydroxide (Ca(OH)2) reacts with hydrochloric acid (HCl) and form calcium chloride (CaCl2) and water (H2O). This reaction is a weak base - strong acid reaction. Ca(OH)2 is a white precipitate and HCl is a aqueous solution. When reaction occurs, white precipitate is dissolved and colouress solution is given.


In this tutorial, we will discuss followings.

Reaction of Ca(OH)2 and HCl and balanced equation Reactants of reactions Products of reactions Change of oxidation numbers Physical and chemical properties changes during the reaction Health, safety measures of Ca(OH)2, HCl and CaCl2


Reaction of Ca(OH)2 and HCl and balanced equation

  • As mentioned earlier, calcium chloride and water are given as products. Because Calcium hydroxide's solubility is low in water, Ca(OH)2 partially dissociates to Ca2+ and OH- ions. Therefore there is very low OH- concentration in the aqueous solution which contains Ca(OH)2.
  • But, HCl is readily soluble in water dissociates to H+ ions and Cl- ions and form a colourless solution.
  • Now, there are H+ ions and OH- ions due to dissociation of Ca(OH)2 and HCl. So, now neutralization reaction takes place as figured below.
reaction of Ca(OH)2 + HCl = CaCl2+ H2O

Balanced equation of Ca(OH)2 and HCl

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

According to the balanced equation, one mole of Ca(OH)2 reacts with two mole of HCl and gives one mole of CaCl2 and two moles of H2O respectively.



calcium hydroxide and hydrochloric acid Ca(OH)2 + HCl

Explanation of dissolving of Ca(OH)2 by the concept of Equilibrium

Initially there are limited OH- concentration in the Ca(OH)2 solution. When HCl acid is added, hydroxyl ions received from Ca(OH)2 and H+ ions which are received from HCl react with each other. Then OH- concentration is reduced. According to the Le'chatalier principle, to keep the equilibrium, Ca(OH)2 is dissolved to release more OH- ions.



Reactants of the reaction: Ca(OH)2 and HCl


Calcium hydroxide (Ca(OH)2)

Calcium hydroxide is a white solid at room temperature and not much soluble in water. There is a very less amount of OH- concentration in a aqueous solution which contain Ca(OH)2 precipitate.


Hydrochloric acid (HCl)

Hydrochloric acid is a strong acid and highly soluble in water. It dissociates completely in water.



Products of the reaction: CaCl2 and H2O


Calcium chloride (CaCl2)

Calcium chloride is soluble in water and give a colourless aqueous solution.



Change of oxidation numbers

Oxidation numbers of atoms are not changed during the reaction. Therefore, this reaction is not a redox reaction.





Physical and chemical observation of Ca(OH)2 and HCl reaction

Here, we will see some physical observations and chemical properties changes during the reaction.


Colour and physical state changes

  • Because Ca(OH)2's solubility is low is water, you can see a deposited white solid at the bottom of the solution. HCl is a colourless solution.
  • CaCl2 is soluble in water and give a colourless aqueous solution.



Safety, health hazards and environmental impacts due to Ca(OH)2, HCl, CaCl2

  • Ca(OH)2: Corrosive, irritant
  • HCl: Corrosive, Acute toxic
  • CaCl2: Irritant


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