caoh2 + h2so4

H2SO4 + Ca(OH)2 is a reaction between a strong acid and a strong base. Let us discuss some great facts about this reaction in this article.

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H2SO4 is the king of acids and is also commonly known as the oil of vitriol. It is used variously, such as in cleaning other metals and manufacturing different chemicals, dyes, etc. Ca(OH)2 is produced when CaO (quicklime) is combined with water. It is white and in crystalline sườn.

With the help of a completely balanced chemical equation, we will know various aspects of this reaction lượt thích reaction enthalpy, type of reaction etc. 

What is the product of H2SO4 and Ca(OH)2

CaSO4 (Calcium Sulphate) and H2O (water) are the two products which are formed when H2SO4 and Ca(OH)2 react with each other.

Ca(OH)2 + H2SO4 → CaSO4 + 2H2O

What type of reaction is H2SO4 + Ca(OH)2

H2SO4 + Ca(OH)2 is a neutralization reaction in which a strong acid reacts with a strong base to tướng sườn a corresponding sparingly soluble salt.

How to tướng balance H2SO4 +Ca(OH)2

  • Write the complete skeletal chemical equation.
  • Write the name of all the elements present in the chemical equation.
ElementsNumber of atoms on reactant sideNumber of atoms on product side
Number of atoms
  • Equalize the number of atoms on both reactant and product side.

H2SO4 + Ca(OH)2 titration

Titration of H2SO4 with Ca(OH)2 in presence of phenolphthalein is an example of acid-base titration.

Apparatus used

  • Graduated Cylinder
  • Burette                                                                   
  • Phenolphthalein
  • Volumetric Flask (helps in storing the solution)                    
  • Ring stand
  • Small funnel
  • Erlenmeyer Flask (Titration field)


The indicator used in H2SO4 + CaSO4 reaction is Phenolphthalein because it easily changes colour in a defined pH.

IndicatorColour in normal conditionColour in basesColour in acids
Phenolphthalein Pinkpinktransparent
Change in color of Phenolphthalein


  • Ca(OH)2 of unknown molarity is added to tướng the Erlenmeyer Flask.
  • Next step is to tướng add 2 drops of Phenolphthalein.
  • The color change needs to tướng be recorded simultaneously.
  • 3 Molar of Sulfuric acid is diluted to tướng a low concentration.
  • Burette is used to tướng add few droplets to tướng the analyte.
  • The solution is being stirred continuously.
  • When colour starts appearing, slow down the rate of droplets in order to tướng get the precise result.
  • When the colour starts appearing as light pink, record the amount of titrant used to tướng calculate the concentration of your analyte
  • For each different concentration of Sulfuric Acid, repeat the same steps.


The results of titration of H2SO4 and Ca(OH)2 are unreliable as the concentrations vì thế not remain stable because the external factors cause unstability in the trials. The colour formed does not depend upon the solution taken; rather, it depends upon the indicator taken hence, the colour formed is pink.

H2SO4 + Ca(OH)2 net ionic equation

The ionic equation for the reaction is,

Ca2+ + 2OH + 2H+ SO42-CaSO4(s) +2H2O(l)

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The net ionic equation is derived using the following steps:

  • Write the complete balanced equation.
  • Ca(OH)2 + H2SO4 → CaSO4 + 2H2O
  • Add the physical states of the compound along with them.
  • Ca(OH)2(aq) + H2SO4(aq) → CaSO4(aq) + 2H2O(aq)
  • Break all the compound which are soluble in water into their respective ions.
  • Ca2+ + 2OH + 2H+ SO42-CaSO4(s) +2H2O(l)
  • Cross out the ions which are similar on both reactant and product side.
  • Ca(OH)2(aq) + H2SO4(aq) → CaSO4(aq) + 2H2O(aq)
  • The equation left is the net ionic equation.  
  • Ca2+ + 2OH + 2H+ SO42- →CaSO4(s) +2H2O(l)

H2SO4 + Ca(OH)2 conjugate pairs

  • H2SO4 is a strong acid and its conjugate base is HSO4
  • The conjugate acid pair of Ca(OH)2 is Ca(OH)+.

H2SO4 and Ca(OH)2 intermolecular forces

  • There are three types of intermolecular forces between the molecules of H2SO4: van der Waals dispersion forces, dipole-dipole interactions and hydrogen bonding .
  • Ca(OH)2 is an ionic compound with strong forces of attraction between its ions.

H2SO4 + Ca(OH)2 reaction enthalpy

 The reaction enthalpy of H2SO4 + Ca(OH)2 is -23.61 kJ.

Is H2SO4 + Ca(OH)2 a buffer solution

The reaction between H2SO4 and Ca(OH)2 can not make a buffer solution because this is a neutralization reaction and will ionize completely.

Is H2SO4 + Ca(OH)2 a complete reaction

H2SO4 and Ca(OH)2 are complete reactions because reactants exchange their ions mutually to tướng sườn two products.

Is H2SO4 + Ca(OH)2 an exothermic or endothermic reaction

The reaction between H2SO4 and Ca(OH)2 is highly exothermic because the reaction enthalpy is very high; hence, a lot of heat has evolved.

Is H2SO4 + Ca(OH)2 a redox reaction

The reaction involved between H2SO4 and Ca(OH)2 is not a redox reaction because there is no change in the oxidation states of the elements, which is explained below.

Oxidation states of the elements

Is H2SO4 + Ca(OH)2 a precipitation reaction

This is not a precipitate reaction because no precipitate is formed when H2SO4 combines with Ca(OH)2. It forms a soluble salt instead.

Is H2SO4 + Ca(OH)2 reversible or irreversible reaction

The reaction between H2SO4 and Ca(OH)2 is reversible because this reaction tends to tướng move in both forward and backward directions.

Is H2SO4 + Ca(OH)2 displacement reaction

When H2SO4 combines with Ca(OH)2, double displacement takes because there is a mutual exchange of ions. Ca combines with SO42- ions and H+ combines with OH ions to tướng sườn water.


The Ca(OH)2 and H2SO4 is an acid-base reaction; hence, the products formed are salt and water. The salt, CaSO4, causes permanent hardness in water and is used as a dessicate. H2O has pH 7 and hydrogen bonding between its molecules.

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