15 Facts on HI + CaOCl2: What, How To Balance & FAQs

Chemical reactions are the interactive process of reactant species in proper orientation to produce new compounds. Let us explore the chemical reactivity of HI and CaOCl₂.

HI, is a strong acid which is generally a gas under standard conditions. It is used as a reducing agent for various organic syntheses. CaOCl₂ is the main component of bleaching powder used in water purification processes.

The reactivity of HI and CaOCl₂ produces deliquescent solid salts used in the photographic industry. In addition, these important mechanism-based characteristics of the reactants are studied as under:

What is the product of HI and CaOCl₂?

HI and CaOCl₂ interact to produce calcium iodide (CaI), chlorine gas (Cl₂), and water (H₂O). The complete chemical equation is given as:

HI + CaOCl₂ = CaI + H₂O + Cl₂

What type of reaction is HI + CaOCl₂?

HI + CaOCl₂ is a displacement reaction followed by redox reaction where chlorine from CaOCl₂ is displaced and later is oxidized after getting free.

How to balance HI + CaOCl₂?

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

HI + CaOCl₂ = CaI + H₂O + Cl₂,

• 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 CaOCl₂ + B HI = C Cl₂ + D CaI + E H₂O
• 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.
• Ca = A = D, O = A = E, Cl = 2A = 2C, H = B = 2E, I = B = D
• The Gaussian elimination and substitution methodology is applied to simplify all the variables and coefficients, and the outcomes are
• A = 1, B = 2, C = 1, D = 1, and E = 1
• Hence, the overall balanced equation is,
• CaOCl₂+ 2HI = Cl₂ + CaI + H₂O

HI + CaOCl₂ titration

HI + CaOCl₂ system is not performed as titration because hydrogen iodide (HI) is a gas in standard conditions whereas one requires liquid or aqueous solutions for estimation using titration.

HI + CaOCl₂ net ionic equation

The net ionic equation of HI + CaOCl₂ is

2H⁺ + I^– + Ca⁺² + OCl^– + Cl^– = Ca⁺² + I^– + Cl^– + H⁺ + OH^– + Cl₂(g)

The net ionic equation is obtained using the following steps

• Write the balanced chemical equation and designate the physical states of reactants and products accordingly
• CaOCl₂ (s) + 2 HI (l) = Cl₂ (g) + CaI (l) + H₂O (l)
• Now, strong acids, bases, and salts dissociate into ions whereas pure solid substances and molecules do not dissociate
• Thus, the net ionic equation is
• 2H⁺ + I^– + Ca⁺² + OCl^– + Cl^– = Ca⁺² + I^– + Cl^– + H⁺ + OH^– + Cl₂(g)

HI + CaOCl₂ conjugate pairs

• Conjugate pair of strong acid HI is I^–.
• Conjugate pair of base CaOCl₂ is HCaOCl₂⁺

HI + CaOCl₂ intermolecular forces

Intermolecular forces acting on HI and CaOCl₂ are:

• HI interacts using strong hydrogen bonding, weak London dispersion forces, and dipole-dipole interactions among the molecules.
• CaOCl₂ interacts forming ion-dipole intermolecular bonding between Ca⁺² and OCl₂^– ions.

HI + CaOCl₂ reaction enthalpy

HI + CaOCl₂ exhibits a negative reaction enthalpy because of the formation of an ionic compound. Thus, heat is liberated to show a negative enthalpy value.  

Is HI + CaOCl₂ a buffer solution?

HI + CaOCl₂ does not form a buffer due to the fact that the buffer is made by weak acid and salt of its conjugate base whereas HI is not a weak acid and CaOCl₂ is not a salt of the conjugate base of HI.

Is HI + CaOCl₂ a complete reaction?

HI + CaOCl₂ is a complete reaction because the stable products namely CaI, water, and Cl₂ gas are produced in the reaction.   

Is HI + CaOCl₂ an exothermic or endothermic reaction?

HI + CaOCl₂ is an exothermic reaction because heat is liberated due to the formation of an ionic compound i.e., CaI which determines a negative enthalpy value.

Is HI + CaOCl₂ a redox reaction?

HI + CaOCl₂ is a redox reaction because iodine and oxygen are oxidized and calcium reduces in the ongoing reaction.

HI + CaOCl₂ a precipitation reaction?

HI + CaOCl₂ is not a precipitation reaction as CaI produced in the reaction is highly soluble in water thus no precipitate is formed when the reaction ends.

Is HI + CaOCl₂ reversible or irreversible reaction?

HI + CaOCl₂ is an irreversible reaction because the products formed in the reaction do not change back into the original reactants when the conditions are kept the same.

Is HI + CaOCl₂ displacement reaction?

HI + CaOCl₂ is a displacement reaction because the anion from the acid replaces the oxygen and chlorine from the hypochlorite salt.

Conclusions

The industrial preparation of CaI from HI + CaOCl₂ in an exothermic, displacement, and redox reaction also liberates water and chlorine gas. Calcium iodide (CaI) has several applications in photographic techniques, in spite of its usage as cat food being a good source of iodine.