HI + H2O = H3O + I2

Balanced Chemical Equation – Solution

2HI + 2H2O → 2H3O + I2

The coefficients show the number of particles (atoms or molecules), and the indices show the number of atoms that make up the molecule. New substances are formed as a result of the rearrangement of the original atoms. As a result of a chemical reaction, atoms of chemical elements do not disappear anywhere and new ones do not appear, their number remains unchanged – this follows from the law of conservation of mass of substances.

Chemical Reaction Information

This is an oxidation-reduction (redox) reaction. HI is a reducing agent, H2O is an oxidizing agent.

  • 2 I-I  2 e  2 I0 (oxidation)
  • 2 O-II + 2 e  2 O-III (reduction)

Reaction Type

Substances that react are called starting materials or reactants. The substances that form as a result are called reaction products.


HI – Iodane

  • Other names: Hydroiodic acid.
  • Appearance: Colorless liquid.

H2O – Water, oxidane

  • Other names: Water (H2O), Hydrogen oxide, Hydrogen hydroxide.
  • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas.




  • Names: Iodine.
  • Appearance: Bluish black or dark purple crystals with pungent odour.
Similar Examples of Equalizing a Chemical Reaction
H2O + HI + (CN)2 → I2 + NH4I + CH2NH2COOH
H2O + Cl2 + HI → HCl + HIO3

Alexander Stephenson

Candidate of Chemical Sciences, editor-in-chief of Guide-scientific.com. Lecturer at several international online schools, member of the jury of chemistry competitions and author of scientific articles.

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