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

Zinc oxide is an amphoteric oxide, and it reacts with HCl. Let us explore the products of this reaction with some relevant topics related to this reaction in detail.

Zinc oxide is insoluble in water, but it gets dissolved in acids (HCl, H2SO4, etc). When it reacts with strong acid, HCl, zinc chloride (ZnCl2), and water are obtained as the product.

Let us describe the change of enthalpy, type, balancing method, and ionic equation of the reaction between ZnO and HCl in this article.

What is the product of HCl and ZnO?

When zinc oxide (ZnO) reacts with hydrochloric acid (HCl), hydrogen is replaced from HCl by ZnO and forms zinc chloride (ZnCl2) and water (H2O).

ZnO (aq) + 2HCl (aq) = ZnCl2 (aq) + H2O (l)

What type of reaction is HCl + ZnO?

The reaction between HCl + ZnO is an example of a neutralization. It is also considered a double-displacement and exothermic reaction (change of enthalpy is negative).

How to balance HCl + ZnO?

The following steps should be followed to balance any chemical reaction-

  • Write the unbalanced equation of the reaction with a right arrow sign as it is not balanced yet. ZnO (aq) + HCl (aq) ZnCl2 (aq) + H2O (l)
  • Determine the mole numbers of each of the chemical species on both the reactant and product sides.
ElementsReactant sideProduct side
Mole numbers of each of the chemical species
  • To balance both sides (reactant and product) the integer 2 is multiplied with HCl on the reactant side to balance the number of moles of hydrogen and chlorine.
  • Therefore, the final balanced equation will be – ZnO (s) + 2HCl (aq) = ZnCl2 (aq) + H2O (l).

HCl + ZnO Titration

Complexometric titration is performed between HCl and ZnO to determine the amount of ZnO and Zn2+ in any solution.


Volumetric flask (100 ml), pipette (10 ml), burette, and conical flask.


The Eriochrome black T (EBT) indicator is used in this complexometric titration.


  1. 0.163 g of ZnO is taken in the 100 mL volumetric flask and EDTA having a strength of 1/50 is taken in a burette.
  2. 25 mL of deionized water is poured into the volumetric flask along with the HCl in the dropwise method until the ZnO was completely dissolved and the volumetric flask was filled up to the mark with distilled water.
  3. 10 mL of the above solution is taken through a pipette and keep it in a conical flask. Add 2 mL NH3-NH4Cl solution and 1 drop of EBT indicator. The color of the solution becomes wine-red.
  4. This solution is titrated with the standardized EDTA solution and the red color turns into blue. A total of three titrations should be done for the accurate value.

HCl + ZnO Net Ionic Equation

The net ionic equation of the chemical reaction ZnO+HCl is-

Zn2+ (s) + O2-+ 2H+ (aq) + 2Cl (aq) = Zn2+ (aq) + 2Cl (aq) + H2O (l)

HCL + ZnO Conjugate Pairs

The conjugate pair equation of the chemical reaction ZnO+HCl is HCl + ZnO = Cl + HZnO+. The conjugate pair of acids is nothing but the anion without the H+ ion and for the base, the ion formed after taking an H+ ion.

HCl and ZnO Intermolecular Forces

The intermolecular forces act on HCl and Fe are-

  • HCl is a covalent compound. Therefore, dipole-dipole force, London dispersion force, and Van der Waals force of attraction are working between HCl.
  • ZnO is an ionic metal oxide. Therefore, the electrostatic attraction force or Coloumbic force is working between the Zn2+ and O2-.

HCl + ZnO Reaction Enthalpy

The enthalpy changes of the chemical reaction ZnO+HCl is -169.1 KJ/mol and this is obtained from the enthalpy calculation of the following three chemical reactions.

  • Equation-1: 2Zn (s) + O2 (g) = 2ZnO ∆H = -696.0 KJ/mol
  • Equation-2: O2 (g) + 2H2O (g) = 2H2O (l) ∆H = -571.6 KJ/mol.
  • Equation-3: Zn (s) + 2HCl (g) = ZnCl2 (s) + H2 (g) ∆H = -231.29 KJ/mol.
  • Equation-4: ZnO (s) + 2HCl (aq) = ZnCl2 (aq) + H2O (l)
  • From equations 1 and 2, and 3 the change of enthalpy of equation 4 is calculated. Therefore, the change of enthalpy of equation 3 is = {(+696.0/2) + (-571.6/2) + (-231.29)} KJ/mol = -169.1 KJ/mol

Is HCl + ZnO a buffer solution?

HCl + ZnO is not a buffer solution as it is a solution containing solid metal oxide (ZnO) and a strong acid (HCl).

Is HCl + ZnO a complete reaction?

HCl +ZnO is a complete reaction asit is expressed with its desired products which are zinc chloride and water.

ZnO (s) + 2HCl (aq) = ZnCl2 (aq) + H2O (l)

Is HCl + ZnO an exothermic or endothermic reaction?

HCl + ZnO is an exothermic reaction because the change of enthalpy of this reaction is negative having the value of -169.1 KJ/mol and heat is generated on the product side. It indicates that the products have more stabilization factors than the reactants.

Is HCl + ZnO a redox reaction?

HCl + ZnO is not a redox reaction because a neutralization reaction cannot be a redox reaction. Zn, hydrogen, oxygen, and chlorine does not change their oxidation states from the reactant side to the product side. Therefore, no electron transfer occurs in this reaction between ZnO and HCl.

Is HCl + ZnO a precipitation reaction?

HCl + ZnO is not a precipitation reaction because no precipitation of any products appears in the reaction medium. Zinc chloride (ZnCl2) is completely soluble in water.

Is HCl + ZnO reversible or irreversible reaction?

HCl + ZnO is an irreversible reaction because the products are more stable than the reactants. Besides that, neutralization reactions are always irreversible as products cannot be converted into reactants.

Is HCl + ZnO displacement reaction?

HCl + ZnO is a double-displacement reaction because, in this reaction, Zn displaces hydrogen from HCl and hydrogen also displaces zinc from ZnO and forms zinc chloride (ZnCl2) and water. Therefore, two displacements occur simultaneously in this reaction.

hcl + zno
Double displacement Reaction


Being an amphoteric oxide, ZnO reacts with both the strong acid as well as the strong base (NaOH) and forms sodium zincate (Na2ZnO2) and water which is also an example of neutralization reaction.

Aditi Roy

Hello, I am Aditi Ray, a chemistry SME on this platform. I have completed graduation in Chemistry from the University of Calcutta and post graduation from Techno India University with a specialization in Inorganic Chemistry. I am very happy to be a part of the Lambdageeks family and I would like to explain the subject in a simplistic way. Let's connect through LinkedIn-https://www.linkedin.com/in/aditi-ray-a7a946202

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