15 Facts on HI + O2: What, How To Balance & FAQs

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HI or hydroiodide acid is an aqueous solution hydrogen iodide gas and O2 is a diatomic gas. Let us throw light on the significant characteristics of the reaction between HI and O2.

Hydroiodide acid, being a very strong acid, has an ionization constant value of ~109. O2 is a colorless, odorless gas that constitutes around 21% of Earth’s atmosphere. Being a very reactive gas, oxygen can form compounds with many elements.

As we move down, our perception of all the vital characteristics of the reaction will be clear.

What is the product of HI and O2

For the reaction HI + O2, the products formed are iodine (I2) and water (H2O).

HI + O2  =  I2 + H2O

What type of reaction is HI and O2

HI + O2 belongs to the single displacement reaction category as iodide ion (I–) is displaced by oxide ion (O2-).

How to balance HI and O2

For the reaction HI + O2, the balanced equation is

4HI + O2  =  2I2 + 2H2O

To acquire the balanced equation, the below steps are needed to follow.

  • The chemical equation for the reaction is
  • HI + O2  =  I2 + H2O
  • The number of O atoms is 2 and 1 on the left-hand side and right-hand side of the equation respectively.
  • HI + O2  =  I2 + H2O
  • Multiply H2O by 2 so that the number of O atoms becomes same on both sides.
  • HI + O2  =  I2 + 2H2O
  • Now, in the above equation, the number of H atoms is 1 and 4 on the left-hand side and right-hand side respectively.
  • HI + O2  =  I2 + 2H2O
  • So, HI must be multiplied by 4 so that the number of H atoms becomes same on both sides.
  • 4HI + O2  =  I2 + 2H2O
  • Now, in the above equation, the number of I atoms is 4 and 2 on the left-hand side and right-hand side respectively.
  • 4HI + O2  =  I2 + 2H2O
  • So, I2 must be multiplied by 2 so that the number of I atoms becomes same on both sides.
  • Finally, the balanced equation is
  • 4HI + O2  =  2I2 + 2H2O

HI and O2  titration

Direct titration between HI and O2 gas is not possible as handling gases during titration under normal laboratory conditions is not practicable.

HI and O2 net ionic equation

For HI + O2, the net ionic equation is not possible as except for HI, the other three compounds- O2, I2, and H2O cannot be expressed as dissociated ions.

HI and O2 conjugate pairs

In the reaction HI + O2, the conjugate pairs are

  • Iodide ion (I–) is the conjugate base of the acid HI.
  • Conjugate pair for O2 is not possible as it is a diatomic gas.

HI and O2  intermolecular forces

In the reaction HI + O2, intermolecular forces are

  • Dipole-dipole and London dispersion forces interactions are present in HI molecule, of which the first one is more important because of the electronegativity difference between H and I atoms.
  • London dispersion forces are present in O2 molecule as it is a non-polar molecule.

HI and O2 reaction enthalpy

For HI + O2, the reaction enthalpy value is -465.6 kJ/mole. It is calculated as follows.

CompoundsEnthalpy of formation (ΔHf°) in kJ/mole
HI (g)-26.5
O2 (g)0
I2(l)0
H2O(l)-285.8
Table representing enthalpy of formation values of all compounds
  • Reaction Enthalpy = ΣΔHf°(products) – ΣΔHf° (reactants)  
  • = [ 2*(-285.8)] – [4*(-26.5)]KJ/mol
  • = -465.6 KJ/mol

Is HI and O2 a buffer solution

HI + O2 cannot be a buffer solution as in a buffer solution; a strong acid like HI cannot be present.

Is HI and O2 a complete reaction

HI + O2 is a complete reaction because, after the formation of products, further reaction does not occur.

Is HI and O2 an exothermic or endothermic reaction

HI + O2 is exothermic in nature as heat is liberated during the reaction.

Is HI and O2 a redox reaction

HI + O2 is a redox reaction, as iodide ion (I–) is oxidized to iodine (I2) and oxygen (O2) is reduced to oxide ion (O2-).

HI O2
Redox reaction

Is HI and O2 a precipitation reaction

HI + O2 is not a precipitation reaction as there is no generation of insoluble salt-type product.

Is HI and O2 reversible or irreversible reaction

HI + O2 is an irreversible reaction as it takes place only towards the product side.

Is HI and O2 displacement reaction

HI + O2 is a displacement reaction as the iodide ion present in HI is replaced by an oxide ion producing H2O.

Conclusion

In conclusion, the product iodine is the heaviest one among stable halogens. Under normal conditions, it appears as greyish-black, shiny, crystalline solid and sublimes to form a violet vapor. Its solubility is poor in water because of its non-polar nature but better in hexane, toluene, carbon tetrachloride, etc.