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

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Calamine or ZnO is an inorganic compound whereas Hydroiodic acid is a strong acid. Let’s us see some facts on the reaction of HI + ZnO;

Metal oxide like ZnO is mainly found in the mineral zincite. The colorless gas hydroiodic acid, also known as hydriodic acid, rapidly reddens litmus and emits dense, white vapors in the damp air.

In this article, we will learn about the intermolecular forces, redox reaction, conjugate pairs, etc of the reaction between HI + ZnO.

What is the product of HI and ZnO?

ZnI2 and water are the product formed when HI reacts with ZnO.

                  HI + ZnO = ZnI2 + H2O

What type of reaction is HI + ZnO?

HI + ZnO is an acid-base reaction, where HI is a strong acid and ZnO is a base and thus a neutralization reaction occurs.

How to balance HI + ZnO?

We have to follow the following steps to balance HI + ZnO-

  • First, write down the general equation for the reaction.
  • Then we determine the state(s, l, g, aq) for each reactant and product.
  • After that, we balance the number of moles of each element on either side of the equation.
  • The reaction is balanced and the balanced reaction is given as –

2 HI(aq) + ZnO(s) = ZnI2 (aq) +  H2O (aq)

HI + ZnO titration

The titration of HI + ZnO is a complexometric titration.

Apparatus

Beakers, a wash bottle, a stirrer, a pipette, distilled water, a conical flask, a volumetric flask, and a pipette.

Indicator

Eriochrome black T (EBT) is used as an indicator in this titration.

Procedure

  • The 100 mL volumetric flask is filled with 0.163 g of ZnO, and a burette is filled with EDTA that is diluted to 1/50 strength.
  • Using the dropwise approach, add 25 mL of deionized water to the volumetric flask along with the HI until the ZnO is completely dissolved and the volumetric flask is filled by distilled water.
  • 10 mL of the above mentioned solution is pipetted into a conical flask. Add 1 drop of EBT indicator and 2 mL of NH3-NH4Cl solution.
  • The solution turns wine-red.
  • It is then titrated with standardized EDTA until the solutions red to blue.
  • After that three readings are taken.

HI + ZnO net ionic equation

The net ionic equation between HI + ZnO is –

2 H+ + 2 I– + Zn 2+ + O 2-  = Zn 2+ + 2 I– + 2 H2O

To write the net ionic equation the following steps must be followed:-

  • Write the balanced equation for the reaction.
  • Then write down the physical state of each reactant and product.
  • 2 HI (aq) + ZnO(s) = ZnI2 (aq) +  H2O (l)
  • HI is a strong electrolyte so it will dissociate completely to form 2 H+ and 2 I+ ions.
  • 2 HI (aq) =  2 H+ + 2I–
  • In ZnO, Zn has a formal charge of+2 and oxide has a formal charge of -1 so it dissociates into Zn2+ and O2-.
  • ZnO (s)   =  Zn2+ +  O2-
  • On the product side of the balanced equation, ZnI2 dissociates into Zn2+ and 2 I–.
  • Thus the net ionic reaction is obtained.

HI + ZnO conjugate pairs

HI + ZnO reaction has the following conjugate pairs-

  • For HI, the conjugate base is I– ion.
  • For ZnO, the conjugate acid is Zn2+.

HI + ZnO intermolecular forces

HI + ZnO reaction has the following intermolecular forces-

  • The forces acting on hydroiodic acid are London forces and dipole-dipole interactions.
  • ZnO is an ionic metal compound so ionic attractive force or coloumbic force is acting on Zn2+ and O2-.

HI + ZnO reaction enthalpy

HI + ZnO has -195.5 KJ/mol standard reaction enthalpy. For the reaction HI + ZnO, the enthalpy of formation of reactants and products are given below-

  • Enthalpy of formation of HI is +26.5 KJ/mol
  • Enthalpy of formation of ZnO is -350.5 KJ/mol
  • Enthalpy of formation of ZnI2 is -208.2 KJ/mol
  • Enthalpy of formation of H2O is -285.8 KJ/mol
  • So, enthalpy of reaction = enthalpy of product – enthalpy of reactant
  • Enthalpy of reaction = [ (-208.2) +(- 285.8)] – [ 2*(+26.5)+(-350.5)]
  • = -195.5 KJ/mol

Is HI + ZnO a buffer solution?

HI + ZnO is not a buffer solution because HI is a strong acid and ZnO is a metal oxide. For a solution to be considered a buffer solution it must consist of a weak acid with its salt or a weak base with its salt.

Is HI + ZnO a complete reaction?

HI + ZnO is a complete solution as no reactant is left at the end of the reaction.

Is HI + ZnO an exothermic reaction?

HI + ZnO is an exothermic reaction as the reaction enthalpy is negative.

Is HI + ZnO a redox reaction?

HI + ZnO is not a redox reaction as there is no change in the oxidation state.

Is HI + ZnO a precipitation reaction?

HI + ZnO is not a precipitation reaction as the salt formed which is ZnI2 is completely soluble in the solution.

Is HI + ZnO an irreversible reaction?

HI + ZnO is an irreversible reaction as we can not reverse the direction of the reaction.

Is HI + ZnO a displacement reaction?

HI + ZnO is a double displacement reaction. As in the reaction of HI + ZnO, Zn takes the place of hydrogen from HI and hydrogen takes the place of zinc from ZnO and forms zinc iodide and water.

HI ZnO
Double displacement reaction

Conclusion

The product formed in the reaction is ZnI2. It is frequently used as an opaque x-ray penetrant in industrial radiography. It improves the contrast between the damaged and intact composite.