15 Facts on HI + Fe(OH)3: What, How To Balance & FAQs

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Chemical reactions generate industrially important compounds with the ability of the reactants to displace their components. Let us explore the chemical reactivity of HI and Fe(OH)3.

HI is a reducing agent which is the strongest acid of the hydro-halides. It works as an important reagent to make alkyl iodides from primary hydroxyl compounds. Fe(OH)3 occurs naturally as different polymorphs namely goethite, akageneite, lepidocrocite, and feroxyhyte.

The reactivity of HI and Fe(OH)3 can be explained in terms of various organic synthesis reactions and metathesis. Furthermore, the mechanisms of different reactions are discussed:

What is the product of HI and Fe(OH)3?

HI and Fe(OH)3 interact to produce iron (III) iodide (FeF3) and water (H2O). The complete chemical equation is given as:

HI + Fe(OH)3 = FeI3 + H2O

What type of reaction is HI + Fe(OH)3?

HI + Fe(OH)3 is a neutralization (acid-base) reaction where acid (HI) and base (Fe(OH)3) reacts together to produce neutral salt (FeI3) and water (H2O).

How to balance HI + Fe(OH)3?

The following algebraic methodology can be used as an explanation to balance the chemical reaction

HI + Fe(OH)3 = FeI3 + H2O,

  • Label each species (reactant or product) given in the chemical equation with a respective variable (A, B, C, D, and E) to illustrate unknown coefficients.
  • A HI + B Fe(OH)3 = C H2O + D FeI3
  • Deduce a suitable equation for each element in the reacting species representing the number of atoms of an element in each reactant or product species, applied to solve the equation.
  • H = A + 3B = 2C, I = A = 3D, Fe = B = D, O = 3B = 1C
  • The Gaussian elimination and substitution methodology is applied to simplify all the variables and coefficients, and the outcomes are
  • A = 3, B = 1, C = 3, and D = 1
  • Hence, the overall balanced equation is,
  • 3 HI + Fe(OH)3 = 3 H2O + FeI3

HI + Fe(OH)3 titration

HI + Fe(OH)3 system is not performed as titration because hydrogen iodide (HI) is a compound that exists in equilibrium as liquid and gas in standard conditions therefore it is not possible for us to use it in the titration experiment.  

HI + Fe(OH)3 net ionic equation

The net ionic equation of HI + Fe(OH)3 is

H+ + I– + Fe(OH)3 (s) = H+ + OH– + FeI3 (s)  

  • Write the balanced chemical equation and designate the physical states of reactants and products accordingly
  • 3 HI (aq) + Fe(OH)3 (s) = 3 H2O (l) + FeI3 (s)
  • Now, strong acids, bases, and salts dissociate into ions whereas pure solid substances and molecules do not dissociate
  • Thus, the net ionic equation is
  • H+ + I– + Fe(OH)3 (s) = H+ + OH– + FeI3 (s)  

HI + Fe(OH)3 conjugate pairs

HI + Fe(OH)3 reaction has the following conjugate pairs:

  • Conjugate pair of strong acid HI is I–.
  • OH– can be considered as a conjugate base of Fe(OH)3
  • Moreover, HI and Fe(OH)3 cannot be considered conjugate pairs as they do not conjugate together to make a new product.

HI + Fe(OH)3 intermolecular forces

Intermolecular forces acting on HI and Fe(OH)3 are:

  • HI interacts using strong hydrogen bonds, weak London dispersion, and dipole-dipole interactions between the molecules.
  • Fe(OH)3 interacts forming electrostatic forces of attraction and interionic Columbic forces between Fe+3 and OH– ions.

HI + Fe(OH)3 reaction enthalpy

HI + Fe(OH)3 exhibits a negative reaction enthalpy of -2356 kJ/mol

  • Bond enthalpy of HI = 297 kJ/mol
  • Bond enthalpy of Fe(OH)3 = 2653 kJ/mol
  • Reaction enthalpy of HI + Fe(OH)3 is calculated as 297 – 2653 kJ/mol
  • The reaction enthalpy comes out to be -2356 kJ/mol.

Is HI + Fe(OH)3 a buffer solution?

HI + Fe(OH)3 does not form a buffer as it is not a combination of weak acid and salt of its conjugate base. Instead HI is a strong acid and Fe(OH)3 is a basic salt.

Is HI + Fe(OH)3 a complete reaction?

HI + Fe(OH)3 is not a complete reaction because the product formed FeI3 is thermodynamically unstable and decomposes in presence of water, heat, or light.

Is HI + Fe(OH)3 an exothermic or endothermic reaction?

HI + Fe(OH)3 is an exothermic reaction because the reaction enthalpy for reaction is calculated to be negative.

Is HI + Fe(OH)3 a redox reaction?

HI + Fe(OH)3 is a redox reaction because HI loses the proton considering an oxidation reaction whereas Fe(OH)3 loses the OH– ion referring to a reduction reaction. As both, reactions occur simultaneously it is a redox reaction.

image fe
Representation of Redox Reaction

HI + Fe(OH)3 a precipitation reaction?

HI + Fe(OH)3 is not a precipitation reaction as FeI3 produced in the reaction readily dissolves in water thus no precipitate remains in the reaction.

Is HI + Fe(OH)3 reversible or irreversible reaction?

HI + Fe(OH)3 is an irreversible reaction because the products iron (III) iodide and water do not react with each other to produce the original reactants keeping all the conditions same.

Is HI + Fe(OH)3 displacement reaction?

HI + Fe(OH)3 is a displacement reaction because the anion (OH–) from Fe(OH)3 gets displaced to HI by removing I– and vice versa.

Conclusions

The reaction between HI and Fe(OH)3 is an exothermic, double displacement, and neutralization reaction which produces an unstable salt of iron (III) iodide which dissolves readily in water due to its hygroscopic nature. The product also undergoes light-induced decomposition to yield iron (II) iodide and iodine.